I'm glad I'm not alone but is there not yet an answer to this problem?! I am using Monterey 12.2.1, Transporter 1.2.3. Same problem, Transporter appears to freeze when UPLOADING APP when I am uploading any large (for example my TFFast app is 200MB, my little apps go up fine). Then my whole Mac freezes up. I either hard-reboot (no response from Force Quit) or if you leave the Mac a while, it reboots and gives the following message when reopening Transporter: Package (s) cannot be found. The following package could not be found: /var/folders/.... 1217478123-01-038.156.01-1.itmsp. They will be deleted from the queue. iCloud has been updating very slowly recently?! Could there be a relationship between ability to upload using Transporter and iCloud sync status? Please help us Quinn the Eskimo!

FB9952962 (Transporter crashes when UPLOADING APP) Submitted via Apple Developer Feedback Assistant. Quinn kindly also advised : "Transporter is supported by App Store Connect Support rather than DTS. You can contact them by going to the main contact page and then clicking App Setup and Distribution > Binary Delivery and Processing." I have opened a Case with Support and will let you guys all know how I get on! Wish me luck!