I'm in the same boat as you.. applied online in Feb, 2021 and got an email last week for 'missing information'. The email asked me to log in to the online application, update and resubmit. Issue was with the application fee document as I uploaded the wrong pdf (I know, stupid of me!).
When I signed in, I could see the entire application back in my account, most of the info and documents I uploaded last time were still there but not everything. I did pay the application fee in Feb so uploaded the correct pdf. In addition to that, the physical presence calculator was removed so had to resubmit that with current date as it would not accept the Feb date (original application date) anymore. The photo I uploaded last time was still there but there was a change in specification for photo and photographer info compared to what it was in Feb, so I changed both of those as well. Made all of these changes the same day and resubmitted.
Feb applicants were still receiving AORs last week so most probably my application was picked for that, an issue was found and thus I got the request over email. It has been a week and I haven't heard back from them, and I think most of Feb applications have already received AORs by now so there's a very high chance that my application is now technically Aug, 2021 application and will be looked at again with Aug applicants.
After the initial burst with few Dec applicants, processing of online application only picked up speed in last few weeks so applications from earlier this year already waited a long time for AOR. Really disappointed that this error (on my part), have further derailed the process for me.
