just to collate everything together id recommend (as others have said) the following things to do in order
1. new brand name battery
2. board factory reset
3. check others arent having similiar fluctuations (meaning its the paint)
4. check detents and replace if necessary
5. try a different barrel
6. try a different bottle (or a couple, including different output pressures)
7. do a full pull down and inspect all orings and relube with pe grease or a decent dow33 based lube (sleek, dye etc)
8. check hpr reg seat and/or replace hpr seat
9. dwell tune (to much or to little dwell can sometimes mess with velocity) as well as adjusting the sfr
- full oring rebuild: sfr, bolt and hpr
- remove solenoid and check for any damage etc.
if none of these work i would recommend having a planet eclipse tech/tech centre look at it...