If the transformer disappears from your devices list is a known issue. Support told me to rescan the QR code, which made it appear, but then the lighting schedules failed -?would not turn off.
The only fix is to delete all the devices, and then the lighting group - which probably will not delete do to the phantom copy of the transformer in there.
Ultimate fix is to reset the bridge (paper clip in hole to push button, hold for 30 seconds), then re-add in the bridge, and any others. This wipes everything . And why I save all the box ends from my ring purchases, which have the QR code on them Dont create any lighting schedules until all devices are added and in a lighting group.
Then at the lighting group level, select lighting schedule and create. It will let you copy that schedule to other devices.
Also if you’ve added any A19 smart bulbs, those need a hotfix to work correctly, support can apply. They will need screenshots of the Device Health page for each A19 bulb