So I don't believe the disappearance of the progress bar is a technical glitch.
On Monday (10th May), I submitted new scans of our passport as we had new stamps on it (from December last year) from our winter holiday. These came after our application was submitted. I had completely forgotten about these since our application was already in process - but then, when I remembered, I asked through webform if they need to be uploaded, and was told to upload it and let IRCC decide if it was relevant or not.
Last night, I received an email that they had received both our passport-scans and our account was "updated". They also informed us that our eligibility is being processed (we didn't ask) and that they will let us know if they require more information.
Even today, the progress bar is visible. I believe they might have removed the progress bar for those who's decision has been made.
All these people with "decision made" status must be sending webform after webform, trying to find out when they can take their next breath, so they may have removed those progress bars to indicate that there's nothing more to ask for - just wait for your decision email - and stop sending webforms and creating extra work!
So it may not be a glitch but it may be an indicator of "decision made".
EDIT: Unless of course it comes back on your account later - in which case, it is a tech-glitch.