if it was me, the first thing would be to replace the entire directional contactor assembly. what this code means to me is that (most likely, in my experience) the reverse contactor is not pulling in as fast as it should, often due to wear on the guides and insulators. replacing just the tips most likely will not cure it for long, it is now time to replace the entire contactor (maybe not the coils, but the rest of it needs to be replaced).

This assumes the rest of the contactors are all in good to 'like new' condition, and that the battery is clean* and well charged, and does not drop voltage more than 10% of the 'at rest' voltage when in hydraulic stall for 3 seconds.
*='Battery clean' meaning that from _any_ power cable to the frame of the truck has at least 100k ohm resistance with the battery disconnected.