Safari Tab Groups are occasionally deleted/hidden from me

Hello,

I've been running into a strange problem, recently I bought a used iPhone and while setting it up, all my tab groups in Safari were deleted. Thankfully, I was able to restore them, because while they had been removed from my Mac and both the phones (was still using the old one to set up the new one), they weren't deleted from my iPad; I had to "share" each tab group with myself in order to get them back.

I initially thought that something during the set-up process caused this to happen, however a similar thing has just occurred: I moved from working into a tab group and went to some tabs that weren't saved in a group; when I went to go back to the initial tab group, I found that all my saved tab groups were missing. Again, only my iPad was unaffected (as was the old iPhone, with which I safely deleted all my info and sold). However, instead of sharing the tab groups with myself again, I restarted Safari, which magically brought every "lost" tab-group back.

It's great that on both these occasions I've been able to recover my groups, but I want to know WHY this is happening. Out of fear of completely losing all tab groups and not being able to recover them, I've started mass-copying all the links in each group and pasting them into an iCloud note page. This can be done by just right-clicking the tab group, but odds are that I'm not going to remember to do this every time I make a change. It's really quite annoying, because with my understanding of how Safari works, I shouldn't HAVE to manually save each link in a tab-group on the off-chance that Safari decides to hide them or, worst case, delete them entirely.

Some information that might be relevant:

• new iPhone is a 13 Mini, using iOS version 18.4.1*
• old iPhone was an 11, and had been updated to the latest iOS that I could install (did so around 24/04/25)
• MacBook is a 13-inch Pro, 2018, macOS Sequoia 15.4.1*
• iPad is an Air, 4th Gen, using iOS version 18.4.1*
• All tab groups were made on my Mac
• I have no clue as to why only my iPad has been unaffected each time this has happened.
• The only common theme between both occasions has been me switching from a saved tab group to an unsaved tab, on my Mac.

*See 'Software updates' note