Hi! My situation was somewhat similar to yours - I posted my timeline a few posts above. There were issues with my birth certificate and I had to provide both an original and a corrected copy to IRCC, since my father's country of birth was incorrect on the original, and of course that was the only determining factor that made me Canadian!
As for your situation, you said your application was sent to the PSU in December 2023. To give you my timeline, my application was sent to the PSU in late November/December 2022, and I was granted citizenship in August 2023 - it was in PSU about 9 months. In total, it took about 16 months from start to finish, and during 2022, the IRCC normal processing time was only 12 months, so there
was a substantial 4 month delay.
Unfortunately, when you provide the IRCC anything that isn't considered a "normal" application, it gets flagged and sent to the PSU no matter what. In my case it was checking the "yes" box on the question about providing an additional birth certificate that wasn't the original.
This may not be the most hopeful answer, but the only thing you can do is wait!! If you know you're a Canadian citizen from your mother, and you've provided all of the information that proves that, then your citizenship will come with time.
As of today, IRCC processing time for this type of application (when it's normal) is 10 months. Keep checking on your application every few months and also keep an eye on the IRCC's normal processing time for citizenship certificates applications as it gets closer to the summer.
Good luck!!