IMHO Re a diaphragm regulator, it is always good practice to do a quick check of the hp sealing components when the low pressure side is removed-as in the case to replace the -024 o-ring. Simply position the first stage body on a tank so that the diaphragm is facing up. Remove the diaphragm and any thrust washers. Turn on the air and apply a few drops of water in the chamber. If there is a leak somewhere in the hp side you will see bubbling. This takes all of 2 minutes to accomplish and can save you all sorts of time later (not to mention hair.)
See @rsingler 's post linked below for more information:
How to cure IP creep in a Diaphragm First Stage
That's a good approach. I didn't do all that, but I did replace the 024 o ring and that didn't do anything to fix my issue.