After re-opening a MC 2018.1 win7 project, all relinked media are not saved (offline again)

It seems there is an issue with linked media source paths or a possible conceptual misunderstanding here on my side(?) and maybe sth mixed up with another possible old AMA plugin issue I remember with PRORES back in the days coming in the mix, all regarding the relinking of footage clips used in an old sequence, which is strongly required today. Of course...

There are about 12 bins in this project from 2013 (I think it must have been MC 7 then) , most of them named by the shooting/scene groups. All this bins are about some years old and from my memory they all hold AMA-linked clips from back in the days. most of them are 1080i/50 PRORES HQ clips, some are MXF DNxHD 158 and some are comps from other software. The needed sequence is in another extra bin (and it seems the sequence status changes for the moment if temporary relinks are successful).

After such a long time, of course, the HD management has changed, the footage has been moved to backup HDs and the editor has changed too :-) 

So for me it wasn't a big surprise that all media was offline and the sequence was simply red and I had to relink it all. But from there, the surprises won't stop to come in:

 

1. First surpise: I wasn't able to relink drives easely. It says there is nothing to relink? And there is no project management where I can simply say, where the root (HD) of the linked media files is now? Hm. Then I tried to relink files via the "relink files..." submenu on the right mouse click of each media file item. This worked but it took a long time to relink all media files in all bins step by step to see the sequence slidely changing from red to blue, step by step.
2. Second surprise: Some media files were not able to relink at all in one way or the other with the statement that files are not 100% identical. But I am pretty sure they are. I heard of scenarios when files get corrupted by moving them from HD to HD and changing their duration slidely (milliseconds). But they are ok so far. How can I force MC to use them?
3. Third surprise. and the hardest one: after taking hours relinking the media files one by one, I had to find out the hard way, that all this work is gone in the wind when I save/close the project and close MC and reopen it again. [:'(]

Now I start to think about to re-edit the whole sequence in another editor, because I find it quite frustrating that I can't force MC to save the state of relinked media in all the bins at least for the media files it worked for (not to mention the ones I can't relink). But before I decide to cancel my subscription I would like to investigate if there is maybe a misunderstanding on my side regarding the relinking and the media file management of MC on this state which maybe makes sense for some reasons I don't know yet. Since I learned that AMA linking is just linking now and that there are multiple ways to break your projects media management from reading other forum threads, I think there will  be maybe another AAH here and there to bring back my trust in being able to finshing this job in MC. While I maybe have only a half way knowledge about file management in latest MC, I would like to mention that I am involved in pro media computer and video codec development and use many pro audio and video software on any system including Linux. So my issues with latest MC must come from things being different to most other applications I know of and are not caused by misunderstanding professional computer technologies in general ;-) ... I hope somebody can help me to bring light into this. Thanks for understanding my frustration and thanks in advance for every minute you give me to help.