Removing a panel that has been glued to a glass window

Removing a panel that has been glued to a glass window I have a window where the previous owner has glued a snug fitting bit of wood directly to the glass. I would like to remove this wood without breaking the glass, or disassembling the window. I don't know what kind of glue was used, when I have managed to get some out is is a clearish rubbery consistency that you can pull a bit like an elastic band, but it looks opaque white when compressed between the window and the wood. There is a gap of around 2-3mm around one corner, but otherwise it is almost perfectly sitting inside the frame. So far I've using a hair dryer to heat it (no effect). Then I tried using paint remover, since the wood was then painted over, which has revealed a gap of around 2-3mm in places. I've also tried using an adhesive residue remover, which I think is dissolving the glue a little, but I can't get it in the right place and can't get the glue out. I'm really stuck for ideas - can anyone think of anything else to try? And here is it from the other side, you can see the glue on the glass. This is the specific adhesive remover I'm using