Lager fermentation advice

Hi all,
I have a lager on at the moment, OG was 1052 and 25L, and was pitched with WLP800 yeast. Temperature is nice and steady at about 12.2C.
I made 2 xstarter's of 3L each with OG's of 1035 (keeping a little back for another beer) but the amount pitched was very adequate according to the yeast pitching calculators.
Anyway, the wort was brewed on 14/4 and now, after 12 days my gravity is still at 1.020. I have a tilt in my fermenter and I have cross checked this against a sample and its reading correct. The beer has been around this gravity for about 4 days now. Last night I gave it a gentle stir in the hope of encouraging some movement - but this morning there's no change.
When I lifted the lid there was still a good krausen head on the beer and the racking cane was still bubbling away, a bubble every 1 second.
Whats people opinions here? Should I be increasing the temperature to help fermentation and start the diacetyl rest early?
Lagers are new to me so any advice is greatly appreciated. It just seems to me that fermentation has stalled.
The sample tasted sweet as expected at this gravity.
TIA
I have a lager on at the moment, OG was 1052 and 25L, and was pitched with WLP800 yeast. Temperature is nice and steady at about 12.2C.
I made 2 xstarter's of 3L each with OG's of 1035 (keeping a little back for another beer) but the amount pitched was very adequate according to the yeast pitching calculators.
Anyway, the wort was brewed on 14/4 and now, after 12 days my gravity is still at 1.020. I have a tilt in my fermenter and I have cross checked this against a sample and its reading correct. The beer has been around this gravity for about 4 days now. Last night I gave it a gentle stir in the hope of encouraging some movement - but this morning there's no change.
When I lifted the lid there was still a good krausen head on the beer and the racking cane was still bubbling away, a bubble every 1 second.
Whats people opinions here? Should I be increasing the temperature to help fermentation and start the diacetyl rest early?
Lagers are new to me so any advice is greatly appreciated. It just seems to me that fermentation has stalled.
The sample tasted sweet as expected at this gravity.
TIA