For FIVB Beach Volleyball, this is covered by 5.1.5 in the 2022 Casebook:
What should the referee do if a ball landed inside the
line, but obviously the line had been displaced
substantially during a previous defending action?
The 1st Referee should have the line corrected, and
then call the ball “in” or “out”, depending on where
the ball landed.
If the 1st Referee is unable to make a clear decision as to whether the ball was in or out, the rally should be replayed as it would for any other situation where the 1st Referee is unsure as to the correct judgement.
This obvious works a lot better on sand where the ball is likely to leave a clear mark than it does on grass; however as there are no professional level tournaments played on grass "nobody cares".