Sadly we've just lost our Walther expert this year, so you may have a bit of a hunt to find any one who could be recomended for old Walthers, I've heard well of Laurie who resides on here who could help if it does actualy need a repair, but I don't know him.
BUT, it sound as if its only adjustment, Walther triggers old and new have a habit of going out of best adjustment if set up finely and regularly used, yours has the ring of the sear engagement requiring attention. Having shot and looked after Walthers for years and still do, they have fabulous triggers when set finely but then once in a while they go over and need a tweak, this sounds like a matter of resetting the "point" when its gone over, the LGR's did it, the LG300 did it, and the new LG 400 does it! And the KK's!!
If you have an LGR handbook, or if not go to the current Walther site www.carl-walther.de and enter the "Sport" portal, then the "Media centre", and there you will find a copy.
The screw you want is no. 20, its the one of the three closest to the front of the trigger blade, its slightly angled. Screw it out (ACW) half a turn, that should allow the trigger to set, if not turn out another half turn until it does, if it does not set then its either been seriously fiddled with or it has a real problem. When you have it setting, then screw it back in (CW) a 1/16th of a turn at a time until it will not set again and then go back (ACW) a 1/16th which should be setting. When its set, check by bumping the stock with your fist and it should not go off, if it does then take it back out another 1/16th. That should then be set so it cocks, and it should be reasonably crisp, and safe.
Good Luck
Robin