Extension appears to be causing long page loads on CiviEvent configuration pages

We have a site that is experience very long page load times (in excess of 30 seconds for first byte received) on CiviEvent configuration pages such as "Manage Events" and individual event configuration forms.

Xdebug profiling data indicates a large amount of execution time in CRM_CiviMobileAPI_ApiWrapper_Participant_Get->toApiOutput(); on the theory that the slow page load was caused by this extension, we disabled it temporarily and observed immediate improvement. After re-enabling the extension, the slow load time again appears.

I'm happy to share the cachegrind.out files from xdebug profiling if that would help. I haven't done any further investigation other than what's reported above.

Any thoughts on what could be happening here?