SIM module and fingerprint sensor stop when back cover is attached

I recently acquired a Huawei P30 Pro from a friend who couldn't be bothered to fix it. The problem being both an intermittent "no sim detected" issue as well as no fingerprint sensor sensor existing according to My Huawei app. Tried all the usual software fixes (updates, hard reset, safe mode, factory reset, etc etc), no luck.

So I ordered a replacement sim module, opened the back cover of the phone and to my surprise (before doing any repair) the fingerprint sensor came online instantly and the sim registered on the network! I waited two days and all was working fine with no back cover. So I replaced the sim module to be safe. All still good.

I wait a week for some B7000 glue to arrive, in which time the phone was fully functional. I clean off the old glue with isopropyl alcohol, add new glue seal her up and wait 4 hours. I come return to find the original issue (no finger sensor and no sim recognised). Any ideas??? I'm considering just leaving the back cover off and getting a case :-)