Battery pack liberates from holder -> FP crashes and rearrangement necessary


today I was shocked, that my FP2 turned off unexpectedly and even loading it didn’t help. Then I displaced the backcover and noticed, that the battery pack fell out easily by shaking the phone.
I guess this is normal and the battery is pushed in by the back cover (there is a rubber ridge right where the battery sits).

First I reassambled the phone and it turned on again.
Then I tried to reproduce the problem by shaking it and hitting it lightly from above while the screen was upside. It needed some time but finally it crashed again (black screen -> total shutdown).

I’m not absolutely happy with it, but have an easy solution for it.
A piece of thick paper (“flyer”) attached between battery pack and backcover did the trick. It wasn’t easy to hold the paper in the right position while closing the cover, so i fixed it with carpet tape to the battery.
It works fine but I’m a bit terrified, that the glue will dissolve (by heat for example).
I guess that could lead to a mess.

I’d exclude security issues, because the phone and battery shouldn’t reach a high enough temperature for burning etc. or do I go wrong there?
I read some topics about heat problems here and that caused some insecurity regarding my solution.

In general I’m really statisfied with the phone and had no real issues till today (got it some days after newyear). I looked through the topics and read some referring to crashes and battery removal, but didn’t come across anything that really fitted my issue.
But maybe there are some people who have the same problem but didn’t recognize it was just a loose battery…

PS: I’m not used to write in english, so please excuse my strange style.