ISO, gain or shutter changes on its own with ATEM Link
With ATEM Link on, the switcher keeps its own copy of each camera's gain, iris, white balance, tint and shutter, and re-sends it on its own. When that copy does not match what you set, the camera appears to change by itself. See Which side wins?.
A Canon camera jumps to ISO 800 (0 dB) or 1/50
Symptom: one or more Canon cameras switch to ISO 800 (shown as 0 dB in gain terms) and shutter 1/50 or 1/60 a few seconds after you select them, and go back to it every 5 seconds. It looks random because it hits whichever camera is selected.
Cause: the switcher cannot see a Canon body. Its stored gain for that input is 0 dB until Middle Control writes it, typically after the switcher restarts or on an input never adjusted from the app. Middle Control was re-applying that empty value to the camera.
- Middle Control 4.0 or above: fixed. The switcher's stored gain and shutter are no longer re-applied to Canon cameras on their own. Changes made in ATEM Software Control or on a control panel still reach the camera when you make them.
- Earlier versions: turn ATEM Link off on the camera page (tally, Multi View and presets keep working), or after each switcher restart step the ISO once in Middle Control on every Canon camera so the switcher stores the right value.
A setting I changed on the camera body comes back
That is the switcher re-sending its stored value. Turn ATEM Link off before adjusting on the body, or make the change in Middle Control, on a control panel or on the ATEM instead. Canon cameras are a partial exception from Middle Control 4.0: gain (ISO) and shutter changes made on the body hold, but iris, white balance, tint and ND are still pulled back by the switcher.