Why does my text randomly change when i close and open the app?

So basically when i close and reopen the Joplin app on my pc or phone, sometimes text has changed font like it has automatically used the "H1" option on the top of the tool bar.
Another extremely annoying thing is when I've highlighted stuff sometimes when i reopen the app my highlights have disappeared and are replaced with == on each side of my highlights. I have no idea why any of this is happening. ive uploaded a print screen of the highlighting problem ive had.

can anyone help me out?

Joplin 2.8.8 (prod, win32)

Client ID: 19d8e9647c344c94ad19c296219e81e2
Sync Version: 3
Profile Version: 41
Keychain Supported: Yes

Revision: c2a6a13