Your comments

I have been able to reproduce the problem with 3.15 on the bench. 
What has happened with IQANdesign version 3.15 is that an XC10 that uses the module enable property gets status Disabled on the DOUT:s. This status remains on individual DOUT:s, even when the XC10 is enabled. 

The disabled status on the individual DOUT:s gets cleared by re-activating the DOUT (changing the input on the DOUT from false to true)
This bug might have been introduced as a consequence of preparing the version 3.15 for DOUT diangostics on the XC10. (requires a new FW version of XC10 that is not yet released). We will have to investigate.

I believe that you have used a module enable on the XC10 to handle another already know problem, that with quick restarting of the system,the MD3 powers up before the XC10 is ready?

A workaround for the moment could be to block the inputs to the DOUT when the XC10 is not enabled. The deactivated DOUT:s will still show the disabled status until activated, but if you use this workaround, you should not see any issues with the functionality.
No, the storage temperature is -40°C. If you go below storage temperature, there is a risk of freezing the liquid chrystals, which would cause permanent damage.
But you can switch on the MD4 at -40°C. The MD4 will start, but the display won't be readable until the heat geneated gets it to about -30°C.
The IQAN-MD4 has a wider temperature range than the IQAN-MD3, so on the MD4, we have not seen any need to add a software function for shutting down the display at extreme temperatures.

Also note that in the MD4 instructions, there are two temperature ranges stated.

Ambient temperature -30 to 70 °C, this is the recommended ambient operating temperature.
Storage temperature -40 to 85 °C

What these numbers don't reveal is that especially in low temperatures, it is the storage temperature that is the important number for avoiding damage to the display.

Starting up the display at -40 °C is not really damaging it, but the MD4 display may not be usable until it is > -30°C.

At high temperatures, you will be able to use the MD4 display outside of the operating range, but colors may not be correct. Also, when combining high temperatures (outside of the operating range) with moisture, there can or will be damage to the display.  
The MD4 +70°C is given as the recommended maximum ambient (surrounding) temperature, to have margins to the display component temperature, since component temperature will be higher than ambient.
I would belive this one is really two separate features. The title suggests that the CAN frame is "extended", but what you actually have to do to send a string that is >8 bytes is to use a protocol that splits up the message over several CAN frames.

In J1939, this can be done with the Data Transfer Message (that we use when reading DM1/DM2)

As the request also mentions GFOUT (generic CAN frame out), that would have to be able to support at least some additional protocol, e.g. the methods used to send CANopen SDO:s with >4 bytes of data.
As Arno suggested, the use of a script created in IQANscript will be a good solution here.
This is how a script for getting the log and saving it to various file formats could look like when you create it:

If you want to take it one step further for simplifying for the driver, you could use IQANcustomize to create a different starting page on IQANrun with a direct link to this script, so that the operator can activate the script with just one click.

The script output (log files) will be stored on the PC in a folder you select in IQANrun
That is also an interesting alternative, it looks like a hysteresis functon.
We have found a problem in IQANsimulate 3.15.14 that can cause this symptom. There will be an update for IQANsimulate released this week.
You are right, the MD4 has got a more powerful processor than the MD3. The reason that we limited the MD4 cycle time to 25 ms as the lowest value was that we saw the cycle utilization (percentage of cycle time used for calculating the application) was fluctuating more than for the other master modules. 
To be sure that also the MD4 would have good real time performance and consistently complete calculating the application every cycle, we put some extra margin on the minimum cycle time.

The graph below is an illustration of this. This exampel is from one MD3 and one MD4 application with as similar applications as possible (the wheel loader example), set to 25 ms and combined in a multi-master system.

The larger fluctations on the MD4 comes when navigating between display pages. Still, in this example the cycle utilization of the MD4 stays below that of the MD3 with an equivalent application the whole time.
We are looking at wheter we could decrease the minimum cycle time of the MD4.

For the specific application example, I am thinking that there could possibly be another factor that limits the reaction time in your system. 
Are you brining in the frequency as a FIN channel, or are you reading the signal via the PCNT channel?
When using the PCNT channel, you get the accumulated pulses every cycle.
When using FIN, the frequency is calculated based on the pulses accumulated with a 50 ms cycle and a moving average filter with time depth 10. This means it averages out the frequency based on the pulses the last 500 ms.
You can get a faster update on the frequency signal by using the PCNT channel, attached is an example: l Pulse count to frequency.ida3

You could also split up the application and use e.g. an MC2 for the faster control loop.
What filter to choose and how to tune it will depend on how quickly you need the filtered signal to respond to an actual change.
Two filter types to try in this case would be the SFC-Moving average, and the SFC-BWL.

The moving average is good to use where there are spikes in the measurement that you want to filter out. It will also filter out these low amptitude oscialltions that you describe. 

If you need to filter out the small amplitude fluctuations, but still react quickly to a step change, then the BWL could be a good choice.

Below is an attempt to illustrate the differences between the filters.There is not much oscillation on the input signal to start with here, but both the moving average and the BWL does a pretty good job in filtering these out. 
The main noticable difference is how they respond to a quick change in the input signal.