When I resume my app sometimes (depends on the memory, AFAIK) the application start with errors (due to images or control not more existant).
If I don't use my application leave it in background (using other application) after lot of time (more than 1 - 2 days or after a week and/or with an intense use of other application) I have some time of problem.
Sometimes on menu, sometimes on bitmap, sometimes somewhere in a control, in whatever forms.
Our program is also very heavy with more than 100 forms, using a lot of libraries (13MB of APK).
It not happens if I use my application after a little (for example happens for me at monday where I use personal application during the weekend).
Some hints?