After running IPS on Red interface for a few hours I noticed that some sites stopped working, for example these two:
https://en.wikipedia.org/wiki/Inverse-square_law
Found that disabling IPS on the Red interface returned normal access to the two sites listed. Then enabled Red again and access still worked but did fail again after a while. Did not try and measure for how long it takes to fail though but it's a number of minutes.
Tried disabling all Rulesets and that did not restore normal access.
Regards
Wayne