Problems with starting a videowriter pipeline

[zyyk78]

Hi!
I've built a recording program for 2 cameras with trigger

But this doesn't always take effect and seems to cause "damage" to the VideoWriter: it prevents the program from writing any files for a period of time, and even restarting the computer doesn't help. So I switched to FFmpeg VideoWriter. It can work once, but it may report an error saying "All pipe instances are busy." after that.

The most peculiar thing is that it usually works fine the first time, but fails next time.
It seems to have relations to dynamic changing file name, but I'm not sure:

This works well ,but below

can just work once ( next time may report an error).However, 1 camera works well with changing filename :

and this can also work:

Does it mean "only 1 filename can be changed" ???Its hard for me to understand at all TAT.
I have tried restarting computer and reinstalling software but it cant work, and i also didn't find a problem in Discussion like this. It seems necessary to wait for a period of time (the length of which is not certain) for the issue to resolve itself..... (but i didn't do anything during that time, just after while).

Thank you!!!!!

[zyyk78]

Update 2024/12/10:

I found this can work
it seems that it cannot work with an "expression" input