Just ran in to this problem on two different sites. After upgrading with update 47 the properties taged with UIHint.Media and backing type Url doesn't save a value anymore.
Anyone else run into this or am I just doing something wrong in both occations?
Workaround is to change to ContentReference as backing type and then change your code accurently
I'll try your fix :-)
Actually, that would be a lot of work in our case.
This is hitting us pretty hard. Hoping for a quick fix..
Know and fixed bug so will be comming in next release.