I have fullrenderplayerlimit set to 1 in the config file so the fullrender pauses when 1 or more players are online. However, the pause feature doesn't always work, and it keeps running even while players are online. This notably happens after a server restart and players rejoin very quickly, before Dynmap has started rendering again.

I've also tried pausing the rendering manually using "/dynmap pause" and "/dynmap pause world" in the console, but all I get is this:

[Wed, 2. Dec 2020 02:30:02 CET INFO] Full/Radius renders are ACTIVE
[Wed, 2. Dec 2020 02:30:02 CET INFO] Update renders are ACTIVE
[Wed, 2. Dec 2020 02:30:02 CET INFO] Zoom out processing is ACTIVE

Nothing gets paused, it just shows which renders are active??

So I either have to restart the server again, which is an annoyance to the players, or cancel the rendering completely to prevent the lag.

If you check out the Wiki, you can see there are only 2 options:
/dynmap pause all: pause all map rendering (updates and full/radius renders)
/dynmap pause none: resume all map rendering

There is technically the 3rd command '/dynmap pause' which shows the statuses you already saw.