Excel4Mac - can't find my VBA modules?

Excel4Mac - can't find my VBA modules?

I have an Excel sheet with several macros, coded on a Windows machine. I
used to keep the file in a dropbox folder for easy sharing with my home
computer, which is a mac.
I never had any problem until now. The VBA modules of the original file
appear to be corrupted so when I try to open the sheet on my windows
computer, I get an error message and then Excel proceeds to delete the
macros. I changed the xlsm file to zip and tried to recover the binary
file, but when I try to read it with wordpad, word, hexreaders etc. it's
just a bunch of messed up code.
On Mac instead it works perfectly fine. Well, not really. When I open the
file, Excel for Mac asks me if I want to activate the macros. I click yes
and the sheet opens fine. Some of these macros are associated to shapes,
so to have a "button" effect. When I click one of these shapes, the macro
associated to it runs just fine, as always, without crashing. However, I
can't see any macro in the macro pane nor in VBA editor. Other info: I
already set the security options to minimum. One of these macros has bugs.
If I click the debug button on Excel for Mac after running it, the program
crashes.
Other content of this sheet is unscathed.
What should I do to recover the body text of these macros either on
Windows or Mac? I'm at my wits end. Thanks!