FVWM: debugging strange behaviour

I have a complex fvwm config that switches between tilling mode and normal mode
depending on the desk/page I'm, it works quite well, but from time to time when
entering a given desk/page some of the windows disappear from it and appear in
another random page in the same desk, this is very annoying.

It just happens once every few hours, and afterwards windows begin disappearing
also from the WindowList although I'm watching them, also their titles in
FvwmIconMan get truncated to just the first letter, for example Xterm becomes
just "X" and so on, but if I switch to another page and come back to the previous
one the problem get fixed temporarily.

The config relies heavily in InfoStoreAdd/Remove statements, variables and
PipeRead, so it well could be that somewhere I'm providing wrong data to fvwm.

So basically I'm trying to enable debugging messages in Fvwm, I have tried with
-D, --debug and --debug-stack-ring but the messages fvwm logs to ~/.xsession-errors
are always the same, not very helpful at all, a few like:

[fvwm][CMD_InfoStore]: <<ERROR>> Bad arguments given.

But as it doesn't say which were the arguments in the first place or at which
line in the config file the error happens, it's hard to locate the problem.

I'm using fvwm 2.6.9., can compile it from source with special options if needed.

Any ideas on how to fix this?

Thank you.