After applying the patches, I've got:

A critical parameter, to_member_id_0, was missing.

when I post to the Forums. I'll try to unwind the patches (I did a backup a few weeks ago)

Reply to Forum Post works fine, but a New post fails with: A critical parameter, to_member_id_0, was missing.

EDIT -------

hotfix-4135, 2020-02-19 5pm.tar causes "A critical parameter, to_member_id_0, was missing." on a New Post to Forums.

I was able to reverse the patch by copying last weeks files specific to this patch, back into place.

That's a wrap on testing and bug reports. That was my wake-up call. If I didn't have that backup, that would be the end of my website and a few months of customizing, and nearly 300 Members (average 6 new per day). I can code a bit, but not enough to fix a weird problem like "A critical parameter, to_member_id_0, was missing." For most people, customizing and fixing light bugs in a CMS is exactly like playing Russian Roulette. I love Composr and I'm looking forward to v11. I'm hoping at that point there will be a database conversion app to convert v10 to v11 fresh install (that's my plan). I've absolutely butchered / slaughtered v10 css, but it allowed me to create the website look I want. I'm hoping that when v11 comes out, I can run an updater for the database only, and then I can correctly edit the css in the right way. In that way, I can take the entire v11 look but keep my v10 database (converted to v11).
 

I'm sorry there was a bug in the fix. It will be corrected before the next patch release is out.

I do not like it when users find an assortment of bugs, but at the same time bigger systems have more potential for bugs.

I do need to stress though that nobody is advocating installing hot fixes without care. Next to each hot fix it says:
"Always take backups of files you are replacing or keep a copy of the manual installer for your version, and only apply fixes you need. These hotfixes are not necessarily reliable or well supported."

v11 will include upgrade capabilities from v10 and should do what you need.

Chris, you are doing such an amazing job! And I apologize if my post was a bit raw. It scared the... stuff out of me to have an error. I have tried to create a community website in the past on several occasions using WordPress and the like, and the site has always bombed out with errors after an upgrade. This time I'm going with Composr because I know it's rock solid. Tempcode in Composr allows me to customize my site without having to code in PHP, and I love the layer of security it offers. This site I'm working on is no longer a trivial site to delete if I get bored. We're almost at 300 Members, and that's really impressive! People are interacting in ways I never could have imagined, and suddenly I have a big responsibility to make sure it's working perfectly. There is no better CMS than Composr for the project, and I'm sorry if I came off in a negative way. You guys/gals are the best.
 

Thanks. I do understand the frustration, I just needed to make our policies clear to anybody else reading.
I've just updated the hot-fix. If you want to check it just make sure you backup any replaced files .