Update: Here what the location bar spits out:
www.mydomain.com/?s=wqsf09be82574&cmf%5B0%5D%5Bmetakey%5D=obj_type&cmf%5B0%5D%5Bcompare%5D=1&cmf%5B0%5D%5Bvalue%5D=wqsfcmfall&cmf%5B1%5D%5Bmetakey%5D=obj_rooms&cmf%5B1%5D%5Bcompare%5D=4&cmf%5B1%5D%5Bvalue%5D=wqsfcmfall&cmf%5B2%5D%5Bmetakey%5D=obj_size&cmf%5B2%5D%5Bcompare%5D=4&cmf%5B2%5D%5Bvalue%5D=wqsfcmfall&cmf%5B3%5D%5Bmetakey%5D=obj_rent&cmf%5B3%5D%5Bcompare%5D=6&cmf%5B3%5D%5Bvalue%5D=wqsfcmfall&cmf%5B4%5D%5Bmetakey%5D=obj_contractlenght&cmf%5B4%5D%5Bcompare%5D=11&cmf%5B4%5D%5Bvalue%5D=wqsfcmfall&skeyword=testing&wqsfsubmit=Search
Update 2: Seems to be a conflict when using Transposh Translation Plugin. Now I have to figure out what’s causing the issue.
Update 3: Unchecked “Allow search of translated languages (and the original language)” in Transposh and now it works again!