I was unable to update the original bug report (#3545160) so I had to create this bug report.
Basically, I applied the patch mentioned in bug report #3528987. That worked (i.e. 'cscope -d -L0 <mysymbol>' returned the proper references) but it only worked temporarily and there's was one exception (see below). After a few days, the same command returned the original error ("Internal error: cannot get source line from database") and the only way to get rid of it was to remove all cscope files and rebuild the database.
The exception mentioned above is that cscope would now find references of the symbol inside CMakeList.txt files, when there were none. I suspect that cmake files somehow confuse cscope after the patch is applied (the symbol in question is identical in name to one of the source files; e.g. 'int foo' and foo.cpp)
I thought I should let you know in case this will help to fix the bug.