it´s most likely the long time in the "hold bath" - water penetrates the sheets from the sides, causing the delamination of the paper base, the two resin coated layers and the emulsion.
I'd have to agree with the above. RC paper requires a minimum of time in solution; enough to get the job done, but not too long. Try skipping that holding bath and go from your fix to wash. Plus, your 5 min. wash is probably too long. Usually there are directions with your paper as to time in each solution. The longest I ever saw for RC paper wash was 4 min.
You are holding the print too long in water. Fiber papers don't suffer from this characteristic, but RC paper is a different animal. If, like me, you don't have running water in the darkroom proper, it's not too hard to get around the problem. All you need is one more tray and hopefully you have room for it. After fixing, give the print a quick rinse in the holding bath and then transfer the print to another dry tray. RC papers don't hold much fixer in the emulsion and the print won't dry out so much that you won't be able to wash it later. Don't worry about a 5 minute final wash. That extra minute won't hurt anything.
I try to keep total immersion time to under 15 minutes for the whole process with RC paper, no problems with splitting. I don't use an acid stop. 2 minutes in dektol, 30 seconde water stop, 30 seconds TF4, 2 minutes wash, 1-2 minutes tone, wash for 3 minutes and done. Works for me, but I wouldn't try this with fiber base.