Reached the end of the road with Stocksubmitter. Due to an incredible amount of bugs combined with the latest months-long Pond5 debacle and the inability of their developer to properly address issues, I started exploring alternatives. Testing IamStocker Studio and Xpiks now. If anyone is aware of other alternative uploaders, I'd like to hear about them, please share the feedback (positive and negative)

Thank you!

Thanks, same here. For now I use IMStudio, it seems like a great deal - 34USD with UNLIMITED uploads to all agencies for the whole year, with autosubmit and great keyworder. It was perfect when I tested it with smaller batches and had some minor issues with bigger batches, but still head and shoulders above Stocksubmitter.
But I wonder about alternatives as well before zeroing in. I vaguely remember another company that charged the same as stocksubmitter with advanced stats and all the bells end whistles but for the life of me can't remember the name.

Can IMStudio also submit videos to all the stock platforms? This has usually been the big challenge over the years

You can upload to all, but submit to 5: IS, P5, Dt, SS, AS.
What I do is the following: fill metadata in IMStudio, export to CSV's from within IMStudio, apply these CSV's in those sites where submission is not supported.. for me, I use CSV's successfully at Envato, Storyblocks, and any other site where IMStudio failed to upload (upload is sometimes buggy).
These days, I never fill metadata manually at any stock site.
For IS and Dt, I still prefer Microstock.plus, as it has unlimited free submissions to these sites. So, upload once to Microstock.plus, and let it submit to both sites... The good thing about Microstock.plus is that it's very stable in upload and submission.