I looked at the April data, since it's about time to post TempLS. And after my experience last month, I now run a simple check on GHCN QCU, just looking at big deviations from average. And yes, there were some.
In Algeria, Mecheria shows -60.8°C. Normal would be 13 (mountains). There is no entry in the CLIMAT form.
Bechar, Algeria shows 0. That is in the CLIMAT, where all temp entries are 0, an obvious error. Normal would be 20.
Port Hardy is back, this time -18.5°C. CLIMAT shows 7.4, but -18.5 for Clyde River, Nunavat. A persistent pattern. Previous similar errors not corrected. In fact, none of the errors (eg Greenland, Denmark) I noted previously have been corrected.
Update. I found another oddity. Last month Greenland showed very high temps, when the CLIMAT form showed no data. Turned out the high numbers entered for March were from Sept, 2013. In April, GHCN also entered data, when there is no CLIMAT form since February. But it didn't stand out as odd. It turns out that it is January 2014 data, which would normally be too cold, but this winter has been warm there.
In March, Denmark got temperatures from last July (hot). In April, it was from January. This is not CLIMAT, which seem right. I guess at this rate May may have caught up.
Fortunately, I can now fix the few spectacular errors. But if I can do such a simple check, I don't know why GHCN can't. And then there are the deviations of about 15°C; I don't know if they are real or not.
Update: I found a contact email at GHCN. I hope they fix it.