Did you brick several OBD adapters by updating firmwares? Or did you have the same problems before flashing? Are you using OBDLINK?
When I got my Huawei P20 Pro, I noticed Scan My Tesla was working very erratically. It worked, but the data was coming in late, in bursts, and often with corrupted values. I then flashed 2 different OBDLINKs with it, and they were both bricked afterwards. Luckily my hunch that The P20 pro had a fishy Bluetooth implementation was correct, and I managed to restore the firmwares on both obdlinks using a different phone (Lenovo P2). I reported this to OBDLINK immediately.
You should contact the support of your OBD2 manufacturer if you're having issues with firmwares etc.
The P20 pro got better for every firmware update after that, and today I am on a P30 Pro with no issues.
Just an idea that maybe you can restore/reflash the firmwares with a different brand phone, just in case your phone has some weird bluetooth stuff going on. Also check for firmware updates for the phone.
OBDLINK LX is my favourite for Android, because it's cheaper but just as good as MX and MX+. Cables from GPS America and EMDS Germany are good quality and each cable is tested before shipping.