@Gregor-Tušar Which version of Moveslink2 do you have? I think 1.5.0 is the latest, but it is available for a while. You might check you HR belt contacts if you have been using for a long time, I just replaced mine (just the belt). Which mobile app do you use: Movescount App or Suunto App?
Never had issues with Moveslink2 on PC and Movescount App on iOS 13 is okay-ish (sport modes change not always sync at first time).