some painters use putty in blemishes, knots in wood ect, same as panel beater uses bog, would ask for photo to help determin but will be without access to computer for a while, only have access at work at present time, try lower heat, maybe a bit more force with scraper, its hard to tell without knowing size of problem, by your post of many layers i would asume lead as many layers indicates age and in old days lead was considered safe, so at this stage i can realy only recomend, persistance, determination and then some more persistance
you mention recessed panel is the goo in corners/joins? if it is i will go putty try wipe a small section with mineral turps it may soften putty to scrape without heat, but make sure its clean again if it does not before applying heat
Bird