Furniture, Wood and Cabinetry Finishing - Paint stripper caused dark stains - help needed

I had been stripping a walnut vanity with chemical stripper (methyline chloride) but ran out late in the day. For the last section I pasted on 3M Safe-Strip, a water-rinse stripper that according to the instructions can be left on for 12-24 hours. The vanity was left overnight in a garage at just above freezing.

Today this last section, plus the already stripped sections that were dripped on, have a lot of what looks like dark water stains. Tried restripping with more chemical stripper but this didn't help much. Now the peice looks ruined. Is there anything I can do to fix this?

I would clean it thoroughly with mineral spirits and let it dry completely. Then evaluate it. I suspect that finishing the job by another round of methylene chloride will straighten it out.

Safest stripper will react with some chemicals. Perhaps some were still on the piece when you changed products.

Oxalic acid (wood bleach) will minimize if not completely remove most marks like you describe. I'd try the solvent based stripper first, just to uniform the surface, but I doubt it will do the job.