Button gets larger

hi,

I dont know if this is an Excel or a Windows issue -- but i believe it's a Windows issue.

In Excel...
1. I created a vba/macro code that does a particular thing.
2. It is attached to a particular button in a particular worksheet
3. The code works fine. It does what i needs to do accurately

Now here is the problem. In 1 out of 10 computers (more or less) where we use the said excel program, stranged thing happens.
1. If I change worksheet views or move to a different window (non-Excel), then go back to that worksheet, the button grows bigger by about 20% from its previous size.
2. This happens even if I dont use the button - just switching views between that worksheet to another worksheet or from that worksheet to another windows.
3. I dont have codes that resizes either the button, the worksheet or even the view.

I think the culprit is the Windows (setup or anything).

Help please?

Thanks,
Aio