I recently was updating mods in my pack and kept running into a clientside crash on startup pointing fingers at Titanium. However, as I tried reading what I could of the errors to see what was being called, I noticed Kotlin and the mods that used it were being called up, I reverted from Kotlin 1.15.0-obf to 1.14.0-obf and the issue cleared up.

Here is a Pastebin with the logs from the console from startup to crash. https://pastebin.com/nqBQY7mh
Please let me know if this is an issue here or if I should create an issue over on the Titanium mod. My assumption is that it's Kotlin possibly due to the fact that I rolled back Kotlin and it worked but it didn't work if I tried rolling back the Titanium update.

The two Titanium versions I was using by the way are
Old: Titanium 1.16.5| 3.2.8.5-19
Newer: Titanium 1.16.5| 3.2.8.5-20

I'll look into it, just archived the file on curse

1.15.1 should work fine

My dude that was the fastest patch and response I've ever seen. Updated to 1.15.1 and was able to launch and get in-game! Thank you very much!