I've got the same issue. Upgraded to v. 4.9.5 and then to 5.2.2.

Couple of errors in the install as below, but not sure they are related. The clue I think is in the reference to ModuleDefinitions.ascx. On a new 5.2.2 install the Host->Moduledefinitions page actually uses extensions.ascx rather than ModuleDefinitions.ascx which has been removed during the upgrade. Something hasn't run correctly to complete this change. Anyone got ideas?

00:00:15.043 -   Executing Application Upgrades: 05.00.00 Error!
00:00:33.289 -   Executing Application Upgrades: 05.00.01 Success
00:00:33.318 -   Executing Application Upgrades: 05.01.00 Error!
00:00:33.471 -   Executing Application Upgrades: 05.01.01 Success
00:00:33.530 -   Executing Application Upgrades: 05.01.02 Success
00:00:33.530 -   Executing Application Upgrades: 05.01.03 Success
00:00:34.174 -   Executing Application Upgrades: 05.01.04 Success
00:00:34.174 -   Executing Application Upgrades: 05.02.00 Success
00:00:34.932 -   Executing Application Upgrades: 05.02.01 Error!
00:00:34.942 -   Executing Application Upgrades: 05.02.02 Success

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Colm Ryan Director
3rd i IT and Business Services Limited

www.actravia.com
Registration and Booking Solutions for Dotnetnuke
www.3rdi.ie
IMCA Registered Management Consulting Practice. Business and IT Strategy, IT Project Management and Product Development

I'm having the same issue trying to upgrade to 5.2.3 and thought it was due to files not getting unzipped, but in checking the zip folder, it doesn't exists ther either.  There is no /ModuleDefinitions/ subfolder in the admin folder at all.  Does this mean that files are missing from the upgrade zip file too?