In the meantime, in Firefox versions previous to 76, you can set the number of Firefox processes to "1" to resolve the issue:
In the Menu bar at the top of the screen, click and select .Click the menu button and select .Click the menu button and select .
- In the General panel, scroll down to Performance.
- Remove the check mark next to Use recommended performance settings.
- Choose 1 in the drop-down menu for Content process limit.