The connection finder itself must be having a problem right now. I also notice a huge jump in the total number of unconnected profiles on wikitree, a much higher jump than I typically see. Typically there's about a thousand more per day, but today I saw that it jumped by about 2.5 MILLION PROFILES!
I noticed this started happening for me yesterday. Profiles that I connected the day before weren't connected like the should be, but the profiles I connected them to are. Now today, they are connected, but profiles I know for a fact are only related to me by marriage are not connected, despite being connected for the past two months. I checked to see if they were still connected to my blood relative who IS still connected, and the relationship is still there.
Also, check out the connection finder. For me, when I see my connection to Emily Bronte or the current member of the week, it now won't consider marriages to be a degree of connection. For example, instead of a piece of a chain saying "woman -> her husband," it now has an extra step, saying "woman -> her son -> his father." I did check and the two parents in the chain are still married.
Hopefully the tech team figures out what is causing this.
In the meantime, it seems that for in-laws to be officially connected to the big tree, the marriage that connects them needs to have children, related by blood to both parties.