It may be the IVAL issue but I ran into something similar running PACControl 9.5 with newer 10+ firmware on the PAC-R1 and R2.
Internally (PACControl) everything worked (I was able to read / write to tags) but when I called up IO in PACControl, I had a similar issues (IVAL and XVAL didn’t agree). Also Inspection of IO points caused loss of communication (on peer to peer communications, PACDisplay, OPC).
In my case I changed the PAC-R firmware back down to 9.5h (last 9.x firmware) and everything worked fine. What firmware is loaded on your the PAC-R ?
I’ve also had weird things happen (didn’t document since I figured I needed to update firmware when problems started) when I had older firmware (PAC-R and PAC-S) on system updated to PACProject 10+.
On older systems (existing pre 10.x PACProject), I’ve been putting in 9.5h on any new or replacements controllers. On newer projects (10.x) or upgrades, I’ve made sure I’ve updated to the newer firmware. We’ve seen less problems since we’ve been recommending this to our customers.