TM M14 not feeding on full auto

[PARALLAX]

Gamed my M14 two days ago, was a beast almost all day but started to have feeding problems only on full auto at the end of the day.

It shoots perfectly fine on semi but will not fire consistently on full auto with any of my mags (all mags are TM).

Generally it will fire 2-3 BB's for every 10 cycles on full auto. If I turn the gun upside down while shooting, the BB's feed perfectly. I however, have trouble believing that all of my mags spontaneously decided to stop feeding properly in one afternoon.

Has anyone encountered a problem like this or have any suggestions?

Thanks

[kotipelto]

I am having this same exact problem, as a matter of fact, my selector switch seems to be stuck only in full auto I cannot use semi anymore. Any help please?

[PARALLAX]

I thought I should add that I recently installed a new hop-up rubber and bucking. Brand is Prometheus purple type, I didn't oil my hop-up when installing.
Could that be the cause of my feed issues only on full-auto? I would expect that I would also see feeding issues on semi, but it shoots perfectly fine. Also the fact that I have no feeding issues when firing upside down has really got me stumped.

Help Please!