Morning/Afternoon/Evening (delete as applicable) all!

Bike: Fuji Roubaix LE (Roadie)

I've been scratching my head with this one for a little while. My chain is jumping whenever I put any force (for example, when in a low gear and wanting to attack a hill, or when in a high gear and wanting to put in a sprint) through the drive train. Typically the chain skips off the front chainrings.

My gut says that this is an indexing issue, but no matter what I try, it persists. The teeth on the chainring and the cassette don't appear unduly worn and the chain looks in decent condition as well.

I picked up the bike second hand about a year ago and it passed an initial service with flying colours, aside from the fact that the rear cassette is a 10-Speed, and the shifters are decades old Shimano-105 11 Speed.

Anyone have any ideas or pointers?