Chain slips off chainrings with a lot of pedal force I have a 2001 Raleigh R600 road bike. It wasn’t ridden much when I got it, and I’ve recently been putting some miles on it. It was a 3x9 speed with 9 speed components. I just changed:

Wheels
Cassette: to a 10 speed with 34t largest (was 28t)
Rear derailleur to a short cage 10 speed
10 speed chain

When I put a lot of force on the pedals (standing up or high gear and push hard), the chain comes off the chainring and makes a grinding/cranking sound.
LBS said components are not compatible, but my shifting is 95% optimal on the rear derailleur. I even can get into the largest cog. If I’m not pedaling with a ton of force, it rides very smoothly and shifts fine. Chain length should be good based on my calculations.
I didn’t change the chainrings, and they could be worn. Is it that or that my components aren’t compatible and it’s misaligned somehow?
I've done something similar - mixing a shimano 105 9 speed triple chainset with a 10 speed chain and a 10 speed cassette and 10 speed derailleur.  It all worked adequately.  It ran fine after a lot of tweaking.
However my chainrings were worn and I had similar slips while climbing.  So I scored some new-old-stock chainrings for the big and middle rings, and all my slipping problems went away.
They happened to be biopace, but that's not relevant.