Fantastic xmf 125 do not accept gas

Hello, I’m writing here on this platform because I just don’t know what to do. I drive a Fantic xmf 125 and was very satisfied with the last 5,000 kilometers and had no problems at all. Since about 3 weeks she only has problems. She doesn’t really take gas, sometimes it works without problems, then sometimes she just goes out in the stand or standing at the ampel. She runs round and sometimes she goes out when giving gas. Sometimes she takes gas and sometimes doesn’t. have already exchanged the lamba probe, the causer and the air filter. Does anyone have idea what else I can do or need to check? Thanks to all the answers I get.