I noticed that ALL that I had in my Dank Storage was lost when I upgraded from 2.7.2 to 2.7.4

I've tested it, created new world on 2.7.2, filled dank with some random stacks, upgraded to 2.7.4 and everything was there just fine. Mod updated between those 2 versions but nothing warns about losing your items so i would guess its some bug with your dank, might be the items you kept.

Interesting. Luckilly for me it was mostly "junk" and replaceable items in it so not the biggest of loss. Just a pain in the *** to gather all them resources once more, like 2 double chests worth of scrap i was saving up for the Matter Fabricator ^^ My bad for not keeping a recent backup, but you have to learn from the misstakes right :)

Try throwing in the Bewitchment Bottle of Blood. It showed up as a "new recepie" for me when I grabbed a botlle from my mob farm. So did also Polished Carbonite from Promenade (but I do not recall having that in the Dank).
I will report if more items show up as "new to me"

Then test with Carbonite and Blunite (Both from Promenade) I know I had a lot of them in the Dank, but it might still be good to try out Bewitched too as noted earlier.

Also noted, but outside this Issue, these seemed to survive an update, but if you downgrade you instance again (a try to get Dank stuff back found on another site) my Carbonite roof vanished :)

Wild explorer also just changed it's name to Promenade and attempted to convert everything to the new modid. So it might be possible that having wild explorer items in it could potentially cause issues. I haven't heard of any issues but I will have to test how well it converts everything.l to the new modid. I don't know that this would cause issues with danks though, usually the items would just disappear.

On the Carbonite roof thing, yes that makes sense. The new mod is only changing overthink over to the new modid. There is nothing in the wild explorer code to change Promenade blocks back into wild explorer blocks, so it assume the mod was removed. When a mod is removed all blocks placed/generated will turn into air, and items will just disappear.

I kind of guessed so, just wanted to share the info :)