It's hard to say without more information.
Do you have a model number, number of batteries used and type of battery (AA, AAA, ?)
Are you sure the blobs are really solder? Can you see any black blobs?
I think that most white LED tourches these days use an LED driver to control them. Some tourches will deliberately have a flashing function. It's alot cheaper to make a driver that does it all and simply not use some of it's functionality when creating different products
In which case it's possible that your tourch has this hidden flashing capability and it has now been activated by some means. Maybe an unproperly terminated input on the chip has "latched up".
Has the tourch got wet or been in a damp environment? It may be being affected by damp. Take it apart and leave somewhere for a while to dryout completely. Probably leaving it outside would work considering the weather.
To get rid of a possible latchup problem, which may well be being maintained by a small residual charge in the chip, take it apart. Remove all batteries and short together any contacts on the PCB for the batteries. Maybe even leave it for a while without the batteries. Charge will eventually leak away.
Are you sure that the new batteries are really new? If there isn't sufficent voltage available then you may get unpredicatable behaviour. Eg. flashing.
Did the tourch cost a lot? There's no guarantee that a traditional tourch wouldn't develop a problem, although it would be easier to diagnose and fix.
Hope this helps.
Note. Please don't short any batteries together!