I doubt that velcro will be of any assistance, and he does not own a Haibike.
On the PCB - There is 12S. which is 50.4V, there is 13S, which is 54.6V, and there is 14S, which is 58.8. The one that matches your PCB of those three is a crapshoot. It is almost certainly NOT for 10S, which would be 42V. If the lack of functionality is indicated by no lights at all, then the PCB is most likely defective, or wired wrong. If the indicator is something different, you will have to explain exactly how it is "not working properly" for a somewhat more educated guess.
As for the lock rattling, the way to get cheap chinese crap to not behave like cheap chinese crap, is to replace it with something that is NOT cheap chinese crap, or at least was made on a different day of the week in the cheap chinese crap factory.