Call woodboilers.com or your Froling dealer and ask for advice. And I have an idea that might work. I suspect, and you probably know, they are stuck because of creosote in the firetubes. More about that in a moment. Are you able to remove the not stuck tubes? If so, or otherwise if possible, you might try blocking the unstuck tubes with a piece of brick, or some other fireproof substance, with the idea of forcing the burned gases through the stuck tubes. Then build a short, hot fire (kindling type material) in the boiler using the bypass damper process, and I mean hot, up to 600-700F flue temp. Then close the bypass and move the boiler into intense gasification and maintain that for awhile, but trying not to get over about 900-1000F flue temp. Just maybe that will burn off the creosote and allow you to remove the stuck tubes. I don't know if the Froling has sensors other than temperature in the exhaust stream from the firetubes. If it does, it is possible that extremely high flue temp could damage those.
As to creosote in the firetubes, even a sophisticated boiler is not immune to creosote from poor burning habits: too wet wood, too cool fire, smoldering wood, delayed gasification, etc. I'm familiar with creosote in a Froling from such burning practices. It is important to improve your burning habits.
