Unexpected variable reset

BACKGROUND:

I’m working with NXP JCOP4 based cards on a custom applet.

At two separate instances I faced that value of a certain variable got reset (I can tell the exact value for only instance and that was 0; I’m assuming that same happened in the second time as well).

This was not at all expected because the variable assignment is done at only one place in the entire source code. Additionally, this part of code becomes inaccessible once the value of this variable changes (and I could confirm that the value actually changed as expected). So I believe it is not a logical bug (otherwise it would occur more often).

The applet on which I’m working is a bit large occupying 17kb of space (on physical cards) for source code and around 10kb of additional memory for installation. In both instances the variables has a scope of “public static” and I was suggested to not use static unless necessary, so I made the change. But I could not recreate the issue in any of multiple attempts to do so.

QUESTION:

Has anyone experienced this type of behaviour on Javacard? Or any mitigation techniques that someone might know.