So are you not having TC mode issues, are you using a DNA75C, and V5, and Lightning cup?
I Actually don't have a 75C... I only have 250C and 100C devices, and they never jump out of TCR when using the V5,or Quest / lighting cup, ever.
One thing you should do, when it's cold, is to re-read the resistance.
This is necessary to see live temperature change, also.
Many themes have an option for this. It can be the Ohm symbol ( Ω not ॐ ), or words, or any other symbol they might use.
I've heard that there have been some issues with some themes because the V5 is a dual coil, and the coils can be off from each other. The fact that it's tungsten makes it change its resistance slighty (in the hundreths and thousandths) each time it's fired. That is, its cold resistance.
So try that, and also try different DNA themes. Other than that, I have no experience with the 75C.
Although your mod has DNA under the hood, some mods can be defective. Some impropetly shielded wire, or other 510 pin issues, can cause problems.
The DNA chip is finicky. It doesnt like the resistance of the 2 coils changing much from each other. As you can see, there is no 'tungsten' mode.
So the chip kicks into Watts mode bcuz the temperatue control fiunction will be off, and it's all about accuracy with DNA/Evolve.
If the mod is servicable, you could check the connections to the 510.
Good luck !
EDIT: OK, sorry , missed your orignal post.
Yes the V4 works because it is a single coil nickel. The Quest works because they are nickel leads.