My exercise calories keep massively changing out of no where and I’m not sure how to fix it.

Quick background: I purchased a Fitbit Charge 5 on 1/11 and have used it everyday since. For the first couple weeks it was great, I was using the Fitbit app for some things and My Fitness Pal to count calories. The past two days MFP drastically drops my exercise calories. For example, today I did a 45 minute workout, walked about 2.5 miles, had 72 “zone minutes” according to Fitbit, and when I got home from the gym MFP said I had earned around 460 calories. An hour later I went into MFP again to log food and my exercise calories had plummeted from 460 to 26. This happened yesterday as well. Any ideas? Nothing else has changed and it worked so well for several weeks.