I'm also experiencing this issue on Mac. I've turned all lock checkboxes off in an effort to keep it from locking and it isn't helping. Seems to be locking after a certain amount of time.
Version 7.4.3.BETA-0 (70403000)
1Password X 1.18.6 on Firefox
If you have Desktop App Integration turned on in 1Password X then it is causing 1Password for Mac to lock, this is a known issue with 1Password X at this time. The only remedy would be to turn off Desktop App Integration, artificially increase the lock after setting in 1Password X and then turn Desktop App Integration back on again.