I believe that you mean ‘DualVerb’ (but correct me if I’m wrong). I’m not sure if this is the problem you’re having, but FREEZE needs ‘something’ in the delay buffer at the moment you press the HotSwitch.
For example, if the reverb has mostly decayed already, you’re ‘capturing’ a low level signal. If your HotSwitch = Off position is a DECAY of 0, it’s easy enough to ‘FREEZE’ silence. When I assign the Off & On (FREEZE) positions to the HotSwitch, I tend to leave a fair amount of DECAY time in the Off position, for two reasons.
One, that will increase my chances of having a strong enough signal at the reverb output to FREEZE (when I press the HotSwitch). A second benefit is that when HotSwitch is switched to Off, there’s a nicely blended fadeout from the frozen signal.
That is, unless an abrupt stop from FREEZE is what you’re after. The ‘sweet spot’ for initial DECAY time will vary … You can try 5 or 10 Seconds to start, in the HotSwitch = Off position. Of course, HotSwitch = On will be the FREEZE position.
Bottom line: engaging FREEZE from zero DECAY can sound like it’s not functioning. I’d never seen the link posted by Russ above in #6, but it has some very useful information on FREEZE / INF, as implemented in various reverb algorithms. The updated link:
https://www.eventideaudio.com/support/downloads/software-500-5-release-notes