if not configuration has changed on the MX and this behaviour has started, I wouldn't start to fiddle around with settings. I'd give Meraki support a call and reproduce the issue - They have elevated rights to get onto the box and see if this is a bug/caching issue with the MX.
If you'd rather try just fixing the issue yourself - try by starting a reboot of the device after hours - Clearing any cache that may have caused the problem.
Eliot F | Simplifying IT with Cloud Solutions
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