Thanks for your hint, @aykolesnikova. My attempts to solve the problem just lead to new issues so far; I might try this too.
By now I was following your advice @jon and used the slider component instead of the rating component, which leads to new problems, since the sliders won’t work out online.
When running the experiment offline the scales look like this:
And here’s what it looks like being run online:
Even the slider’s style is completely different. Is there any solution to this? I already tried changig the screen units, which didn’t make any difference.