Currently not sure the best way to reproduce this but here are the general commands to setup the issue.

Steps to Reproduce

1. /scoreboard objectives add play_timer minecraft.custom:minecraft.play_time

2. /scoreboard objectives setdisplay sidebar play_timer

3. /gamemode spectator @s

4. Check sidebar to see if score stops (I do not believe it should stop and in most cases it wont which is good but if it stops you have encountered the inconsistency)

5. /gamemode survival @s

6. Repeat steps 3 - 5 until you see the score is no longer increasing. Usually for me it stops at the 4th tick

Expected Results: play_time should increase while player is online regardless of gamemode

Actual Results: play_time currently stops "sudo-randomly" when switching between survival and spectator mode.