time travelling in GPX tracks?

During a hike last weekend, I hit an area with poor GPS reception.  Not unexpectedly. this created a few bad points in the track ( https://connect.garmin.com/modern/activity/5672794796 ).   I exported the GPX file to try and remove some of them (before I learned about repairing FIT files from user seilogramp).   When removing the bad points, I also noticed about 29 of the good points, with correct location data, have incorrect dates of April 6 2019  or April 7 2019, while the remaining 986 points have the correct date (Oct 11, 2020).  

I was just curious if this is a known issue with the 66i?   It does seem like a bug so maybe it will be fixed in newer firmware?   

5665450257.zip