Well i found this thread by chance by Ctrl+F ing to get to the Pathpilot topic of the forum.
I had that problems also at those version... Lucky i kept note of my updates ... here they are
/*********** Warning *******/
ALWAYS BACKUP EVERYTHING BEFORE UPDATE
1. After applying the update , DO NOT START PathPilot
2. Copy the New Folder version into the operator folder if its not there yet.(for some reason it often shows up inside the current version folder)
3. Copy file Tormarch_g540.bit in the Mesa folder of the New version
4. ---------
5. Note: Finally got around to fix the BASE.ini file so we should be OK for the future.
6. Compare new BASE.ini file with The custom one. if all good ... copy on config folder
7. Compare Mesa Hal file also .. if all good copy to config folder
8. Start Pathpilot
9. Should be good from here.... Note : didnt need to modify Hal file from V2.3.4 to V2.3.6
10. The V.2.3.4 to V2.3.6 went smooth date ~Oct 31 2019.
11. the V.2.6 to V.2.4 went well. somewhere in 2019 or 2020
12. the V.2.4 to V.2.5 went very bad. Reinstalled V2.0 fresh and did the V2.5 went ok after
13. we are on V.2.6 and did not do the no 4 point so i will strike it . 17 Aug 2020
14. The V.2.6 to V2.7.1 went well by following this procedure. January 8th 2021
15. The V.2.7.1 to V2.7.2 went well by following this procedure. March 28th 2021
16. The V.2.7.2 to V2.8.1 went well by following this procedure. March 28th 2021
17. The V.2.7.2 to V2.8.3 went well by following this procedure. October 17th 2021
Hope this helps