When its playing same pattern in loop - every time with beginning of pattern it “trigger” play button - or maybe pause. In effect some notes are not played on position 00, particularly looped ones.
Try the numpad enter key to turn off block-loop mode if you have triggered that one (that is my second guess).
If you are on a laptop, you might have turned on the numpad functionality using the fn key and the calculator key. It may also change the function of the enter key to send the keycode of the numpad = and renoise responds different to a numpad enter sign
Otherwise simply scan the whole line in the pattern up to where the pattern plays and search each effect column if there is something typed there that you don’t need…