this happens for me when using the 2015 version of the client. i used to use this so if i got an MMS i could still see it in WinMo messaging since it still keeps that portion in tact. the issue is, after deleting sms or receiving an mms you will soon get the screen 'Message Restoring' when you try to access HTC Messaging client. basically you won't be able to access the list of every1's convos or send a new message (since thats controlled by the client) unless you go through WinMo messaging, but you can still access the last 25 text messages and reply to those through the Sense Tab. I assume this is the HTC Messaging Client attempting to update and organize the text messages in relation with the WinMo client. I can attest that this screen may last after multiple soft resets and for more than 24 hours...this at least was my case multiple times and more than likely i ran a Clear Storage and reset up my phone to get this out of the way rather than wait.
For this reason i use the 2018 version from
here. I have yet to run into that problem, the only issue is i have yet to test and see if MMS is working. The developers words were that stock GSM TP2 ROMS have the client incorporated, but no CDMA stock ROMs do so that should be something we think about before installing it. I guess that means they will try to get MMS working for CDMA but we shouldnt be too optimistic at this point.