Check to see if there's a loose brace underneath then.
Seriously, I have similar issues with a 1970s era Takamine that was my prized guitar in the years leading up to my first solid wood guitar. It had the belly bow and even binding coming off at the neck joint. I took it to a tech who told me the cost of a traditional neck reset would cost more than the value of the guitar. He offered a "plan B" for 1/3 of the price and I went with it. A week later my guitar was like new but after several years the bridge started lifting again even though I stuck with light guage strings as the tech instructed. A cracked X brace beneath the treble side bridge wing was the cuplrit and it was causing a noticeable buzz. As for the neck joint, it appears that he used either marine epoxy or CA glue and he was not neat with it.
I had grand designs of steaming off the neck joint and re-topping the old girl but alas a couple of beers greatly ehanced my daring but subdued my caution and intellect. I never got the neck off. In short: I destroyed the neck trying to work it free because while I applied steam I had done so at the wrong point and the epoxy wouldn't have let go anyway. I'll let the pictures tell the rest of the sad tale:
Glue slop from the previous repair:
My first mistake: using the "cold chisel" method of removing the bridge, but in my estimation both the top and the bridge were going bye-bye anyway
I opted to try the neck reset and retop the guitar because the next had considerable drop-off:
Sooooo, I took it over to my friend's house where he has the special tools needed to pull the neck - and a capuccino machine to appy steam:. THe thing is though that the aforementioned beer dulled both our senses and I pulled the wrong fret:
After about 10 minutes of accompishing nothing more than clearing our sinuses I put the guitar in the jig and proceeded to pound away at the heel cap with a fretting hammer. Piece began to fly and my sanity came apart as did the neck and 20 years of memories. I think I was madly singing Maxwell's Silver Hammer as I did this:
The moral I took from this story was almost literally "don't bite off more than you can chew" - or more appropriately don't take a hammer to a prized momento. Now the guitar sits in its case awaiting its ultimate fate while I work carefully try to complete a scratch guitar build and collect materials to build another rosewood dreanought. Like Freeman, I've decided that building a replacement from scratch might be easier. I intend to strip the old Tak for parts and will use its case to house its successor that now resides in my basement in the form of planks:
BTW, I did the Bridge Doctor thing several years ago. I wish I'd learned a little more about woodworking first and was more appreciative of the immense stress that the bridge is under though. I used one of the drill-in types and my major mistake was tightening down that screw too quickly as it split the bridge along the grain. It did solve the problem otherwise and I dare say that it did mellow out the guitar's tone somewhat - but on a dread that I was advised not to use medium gauge strings on that's not necessarily a good thing. It increased the mass of the guitar which IME reduces its resonance, which on a laminated guitar glued together with crazy glue is not necessarily all that good to begin with. If I had to describe the tone, I'd say it was along the lines of an older Breedlove Atlas AD25SR but quieter. It was an interesting experiment though and I chalked it up as a learning experience.