So, possibly they blew through their altitude on the departure, which would have prompted "possible pilot deviation, call ..." from NORCAL.
Look at their track on flightaware. At time 17:30 on the KSJC-Dep archive you can hear N26GP check in with Departure and report "2.7 climbing for 5", then at 18:45 (75 seconds later) they ask "do you want a heading of 300", at which point the controller gives them an immediate right turn to heading 090.
The LOUPE1 departure specifies climb runway heading to 1.8 DME from the SJC VOR then turn right to heading 120. It would appear from their flightaware track that N26GP maintained runway heading (300) until around 7 nautical miles from the SJC VOR before they started to turn. Now why did they stay on the 300 heading, was it an instruction from Tower or maybe some confusion on the position of the overshooting ASA876 ?
By maintaining the 300 degree heading N26GP's track appeared to put them into conflict with traffic landing on runway 28R into KSFO. At time 16:45 on the KFSO-Final archive you can hear AAL881, a Boeing 737-800, report the Bridge in sight and then cleared to 4000, then 5 seconds later cleared for the visual runway 28R. Then at time 18:00, AAL881 reports they are responding to an RA (TCAS Resolution Advisory), then shortly after they are cleared to a heading 360 and cleared to 6000, then vectored around for another approach.
Back on the KJSC-DEP archive at time 19:30, N26GP is told to immediately maintain 4000 feet, then at 20:10, Departure advises N26GP of traffic at 11 o'clock and 4 miles at 4000 a westbound B737.
Speculation on my part, but I suspect that is the deviation ATC is talking about ?