Capitec *****ing from elderly person without a trace

I sent my mother money 500 to be exact through the app and to her surprise she only received 400 and the 100 did not reflect who took it. I searched through her messages and statements but I found nothing. We even went to the branch but this deduction cannot be traced. The same thing happened this month. Is this happening to her because she is an elderly person? Is capitec taking advantage of the old people now? I'm not gonna stick around and watch her being ****med like this especially when she is about to retire.