Should I rebuild a 72v lithium battery

The battery is from a stealth bomber electric bike. It’s 72volts and 24 or more amp hours.
The battery is 4 years old.
It went dead after 500 miles and I bumped it back to life with my lead acid charger. I could always go almost 20 miles range. It went another 500 miles then this summer it dies after a few yards. I tested the individual cells and out of 48 cells 6 have 0 volts and the other 42 have 3.3 volts.
Cells are packets 155mm x 77mm no name just numbers
Should I find these cells and replace them or do you think other cells will fail soon?

It sounds toasted. With the advances in batteries, you could pretty much double your range or halve the size of your pack. Combined with the hassles if trying to balance half new and half failing cells, it might be time...

You could put new cells in with the old cells, but Voltron is right, better to get a new battery. Batteries have gotten much better in 4 years.

Ok, thanks for saving me the expense and heartache!