New update hell...

You should be able to  roll back to the last version . I would be interested to hear if this is an isolated problem. Were templates used from the prior version?

 Probably because a project is associating certain tracks to an instrument that was not registered as VSTi in the current install. Re check your VST paths and make sure all of your instruments plug ins are enabled. Your tracks will re -assign to another instrument if your project can't find the correct one. I think this is what you're experiencing. If worst comes to worst - you will need to re-insert the synth and re-assign the tracks.

quietman
message from Cakewalk...
 
"We've recently had a few users who are facing the issue where they are unable to open their projects or load plugins in properly. Our engineers are already aware of this and are working on an update real soon. We're sorry for the frustration, but we'll reach out to you ASAP or with a fix once we've heard news..."

Hi Martin,
 
I think there was a little miscommunication with one of our support reps. There was a fix related to project MIDI ports that was addressed in the 2018.05 update that just came out. This was specific to adding MIDI ports while a project was currently open.
 
If you are opening a previously saved project, the project MIDI ports should not change and we have not had any other reports of this occurring.
 
If you are seeing this, try seeing if you can open the project normally in SONAR as opposed to Cakewalk by BandLab.  If the project opens correctly there, but not in Cakewalk by BandLab, please PM me with a link to the project and we can troubleshoot it further.
 
Thanks!