Error code 33 is the primary, or low tension side of the ignition coil. First thing would be to check the connections at the coil for corrosion and good contact.

It is possible that there could be an internal fault in the LT side of the coil which would give the same end result.

Either way suspect the coil and/or its wiring to be the issue for a 33 code.

It is also worth noting that (as you say it happened on the sidestand) that the neutral light switch could be faulty? If the switch doesn't close (neutral light on), the bike will think it's in gear and cut the ignition. Does the neutral light work OK? Any flickering or temperamental behaviour?

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