I suffered from mild bruxism about 10 years ago and have had several bouts of TMJD where I couldn’t close one side of my jaw. For me, the key has been poor posture induced by stress; these bouts coincide with heavy laptop and mobile phone use (neck angle forward and down). What fixed it for me was switching to a good desktop set-up whenever possible and self-treatment via Kelly Starrett’s Becoming A Supple Leopard (there is whole section in the second edition on neck and jaw). He has good general advice in this video as well - https://youtu.be/kfg_e6YG37U

I haven’t used the mouthguard now in probably 5 or more years.