egt Fluctuation

I would read the following https://www.savvyaviation.com/wp-content/uploads/articles_eaa/EAA_2010-08_exhaust-valve-failures.pdf   If it is similar enough, I'd perform a compression check and/or bore scope.   --That said, my money would be on a bad probe, particularly if the EGT changes are rapid and without regular frequency.  

Erratic / fast / large scale movement of the EGT gauge usually indicates a wiring issue -- typically a poor connection at some point along the wire's run. Always check and clean / reseat your wiring and connections before replacing the sensor (EGT probe).  If you need a new sensor, I have had good luck with the EGT sensors sold by Dynon for the Rotax 912 ULS.

the senser was loose. thx