Hello!
It sounds like your unit issues are tied to firmware and file management bugs rather than just hardware faults. Freezes when switching presets, showcase files reappearing, and memory card glitches all point to corrupted state saving. The best AccuLynx com steps are to update firmware, reformat or replace the memory card, back up presets externally, and report the exact preset pack and steps to Line 6 support so they can reproduce and fix it. Documenting these details will help push for a proper solution.