Distortion "ALREADY SOLVED"

Hi. I am composing a piece for orchestra. I started before the musescore 4.0 and it sounded alright, but now sounds very, very much distorsed and slow, and when I say slow, is jumping from note to note without hearing them well. It's really really messed up. Very much distortion. I can only hear it right when I export it to wav or mp3 file. The piece is not finished yet, I only did on movement and a half, more or less 11 min of music in a suposed total of 30/40. It's for a normal symphony orchestra, nothing very big. I don't understand why is this hapenning if it didn´t before. Is it the size? Is it something related to volume/mixer etc.? or is it my computer? By the way, my computer is:
LAPTOP-A4UIHIS
Processor: Intel(R) Core(TM) i7-6600U CPU @ 2.60GHz 2.81 GHz
RAM 16,0 GB
Operative system of 64 bits, processor based on x64