I am having a very similar issue... just received my stadium XL yesterday.
1) Bug 1: Preset blocks are not persistent with regard to power state (on/off) once you leave the preset for another preset and return, the power states are not persistent. I finally achieved stable power status on bocks by turning off WiFi and making changes and saving the presets with the floor unit only.
2) Bug 2: The blocks in any of my custom made (from scratch) presets are not persistent - once you leave a preset and return to the preset, all the blocks have returned to default states - this is not solved by the workaround described in item 1 above. There is no workaround I can find for this issue.
3) Bug 3: When selecting blocks in STOMP mode, those blocks DO REMAIN PERSISTANT when returning to preset mode - in other words, I have a preset that has a bock off by design but after using stomp mode where I engaged a block - that same block is still engaged in preset mode when returning to the preset that had the block turned off by design. This crashed the workflow of being able to toggle in/out of stomp mode between preset mode - because your presets will potentially not be where you want them after using stomp mode.
4) FIRMWARE: My WiFi connection is strong and solid so no issues communicating with the unit. I pulled firmware 1.1.0 automatically from the Line6 cloud server as suggested upon startup and initialization from the unit. NO upgrades beyond that version are available at this time to my system.
5) SUMMARY: I could potentially not understand some basic usage protocols for working with this user interface, but I don't think so - I am working in the USER preset area category section. I have also attempted to connect with the unit other than WiFi with no success - the present firmware package does not facilitate this presently to my observation. My first 3 items I have designated a "Bugs" have been extensively tested over 12 hours of continuous work - If I have failed to understand some critical workflow demands to ensure stable persistence of block configuration changes, I would love to hear from Line6 on how I can perform this as it is so critical to operation that the unit is unusable for gigs. I am already in love with this unit though... this is a game-changer once this block persistence issue is figured out... I could easily gig with it in its present state if I could tweak blocks to my desired tones and save them. The tones and workflow are beyond exciting to me - this is an incredible piece of work to be sure. I just need a firmware update to ensure the unit can save presets / blocks properly as designed.