I have discovered that if I adjust my printing speed to be under 100%, then pause and resume the percentage is applied again.
So for example let's assume I'm printing at 100mm/s
Then I set speed to 50% - now it's 50mm/s
Then I pause and resume
Now the UI still shows 50% but the speed is actually 25mm/s
If I repeat pausing and resuming then it gets progressively slower like that.
I guess this is probably not by design?
Running 3.4.5 on a delta printer. Pause and resume macros are defaults from config tool.