"R%8" does not work o UV 14.2.1 as it has for many years

I am not seeing the same behavior.  Something seems different in our environments or I am doing something differently syntax wise but
CRT '1234' "R%8"
returns 00001234 for me in 14.2.1 and also in 11.3.4

To expand on Tyrel’s comment…   We are also running PICK flavor if that is what the issue is.

We run PICK flavor accounts and recently did the upgrade from 11.3.1 to 14.1.1 and have not seen what you’re describing (and we do use this sort of format all over the place).  So either it’s a flavor issue that we’re just not seeing because it doesn’t happen on PICK flavor accounts or what you’re seeing is something that was introduced between 14.1 and 14.2.
Update: We have some machines running 14.2.1 and it’s not happening on our PICK flavor accounts on those machines either.

Just seconding Tyrel and Steven.. not seeing this problem on 14.2.1 either. Anything you can post as an example? What OS are you runining?

Confirming - 14.2.1 and no issue found here in multiple flavours. 
I suggest trying this in XDEMO with a clean compilation and run. Otherwise any customisation in odd environment vartiables or uvconfig?

Also whether Windows or Unix and the version/nationality settings please, also whether you using NLS (which has its own list of setting for various nationality differences) and we can dig further.

Nelson had opened up a support case on this, he is also no longer seeing the issue.

My best guess is it was an input issue.

-Dave