I'm also having the contract spam issue. I get like 100-200 parameter updates frequently. On my end it seems related to my satellite contracts, i.e. any ship I fly that has any of the components required for a satellite (even if I'm doing something totally unrelated) results in fulfilled contact parameter spam. As a very OCD person, I cannot resist acknowledging all these messages even though they are going to come right back when I switch vessels. I will not be making much career progress until the next update it seems.
I tried to revert to 1.4.1 but unfortunately my career save is no longer compatible with this version. (Does anyone know a work around?) I'm new to KSP and was not wise enough to keep a backup save.
Also FWIW, KSP is an incredible game and I'm very happy to see it is still being actively worked on. Thanks team.