In the settlement building browser it shows the tier 2 waystones should take 8 turns. From the campaign map, or if i chose one from the settlement browser, it takes 20 turns for any waystone to upgrade to tier 2. Two screenshots taken on the same turn with nothing being constructed illustrates this. Disabling the building slots mod and dependencies and starting a new campaign gives the proper upgrade times.

https://steamuserimages-a.akamaihd.net/ugc/1934884345506180146/B6637B94467356422AE9A308F02F09FC8D7D5DC7/?imw=5000&imh=5000&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false
https://steamuserimages-a.akamaihd.net/ugc/1934884345506191378/41E1D62EA3EABAFCC6B9781DDC4E633E76FD1D16/?imw=5000&imh=5000&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false

Originally posted by Nylan:

In the settlement building browser it shows the tier 2 waystones should take 8 turns. From the campaign map, or if i chose one from the settlement browser, it takes 20 turns for any waystone to upgrade to tier 2. Two screenshots taken on the same turn with nothing being constructed illustrates this. Disabling the building slots mod and dependencies and starting a new campaign gives the proper upgrade times.

https://steamuserimages-a.akamaihd.net/ugc/1934884345506180146/B6637B94467356422AE9A308F02F09FC8D7D5DC7/?imw=5000&imh=5000&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false
https://steamuserimages-a.akamaihd.net/ugc/1934884345506191378/41E1D62EA3EABAFCC6B9781DDC4E633E76FD1D16/?imw=5000&imh=5000&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false

I've just reproduced this bug without my mods, so this looks like something to report to OvN Team. My mods shouldn't affect any building chains or their build times, because they change completely unrelated tables. Meanwhile, I've found a workaround you can use: start building or upgrading the waystones and immediately cancel it, this will return building time counter back to normal.
Screenshot 1
Screenshot 2

Well that's odd, it had been working properly without the extra build slots mod until i tried to build one, canceled then tried to build another. Over multiple turns they were stuck with the increased build times. I'll see if they will look into it, thanks.