My monk somehow contracted the ooze sickness from his two groupmates, and it caused him to gain movement speed instead of lose it, resulting in him moving over twice his usual speed. When I turned on stealth and detect mode, sometimes he correctly moved slower. I am pretty sure the issue is disease immunity and how the disease is scripted. The disease was contracted on the Canal Depot quest on the last encounter.

The disease bypassing Purity of Body should definitely be fixed in v758.

The speed bug sounds rather weird. I made some changes and hopefully it'll be fixed in v758, but I am not 100% sure on that. Report it in a new thread if it shows up again.