Fermentation is consistently stalling

[TheDudeAbides]

For the second batch in a row, my fermentation is stalling after about four days, with a lot higher SG than I would expect.
Both brews are extracts, both use Brew Cellar dry yeast (Premium Ale and Wheat), and both fermented at around 20 degrees.
I've tried some of the tricks - oscillating the fermenter, warming it up, pitching new yeast - but nothing seems to work.

I am wondering whether I am doing something fundamentally wrong. If anyone could help or give some advice, that would be great. I've detailed the latest recipe and a brief method below to see if anyone can shed some light onto what's going on.

WHEAT BEER
1.5kg DWME
1.5kg DLME
25g Saaz hop pellets
15g Brew Cellar Wheat Beer yeast

50 minute boil with DWME and hops in 6L of water.
DLME added with 10 minutes to go.
Topped up in fermenter to 21L. OG reading of 1.058 (seems very high [.008 above target], but I surmised I didn't mix the wort around enough after adding the water, which gave me an off reading).
Yeast sprinkled on top at 29 degrees. (I know this is too hot, but I was in a helluva rush.)
24 hours later, and fermentation was going crazy with a massive foam layer on top.
Fermented mostly at 20-22 degrees.
SG reading taken yesterday and today says 1.020. Plus, the foam layer is still there (see photo taken five minutes ago).

I'm only thinking there is a problem because I'm assuming my OG reading was off. Brewer's Friend and the recipe suggested my OG should be 1.050 and FG 1.014.

Sorry for the long post. Any help is much appreciated.

 

[manticle]

Is the yeast fresh and kept in the fridge at the brewshop?
Look at buying some proper beer yeast nutrient, look at recommended instructions for yeast rehydration and if looking at kickstarting a stalled ferment, look at making an active starter.

How long has this one been at 1020 and are you measuring with a hydrometer that you know is accurate?

In my experience all extracts do often finish high.

 

[RelaxedBrewer]

It could be your hydrometer is not calibrated correctly.

Test it by putting it in water at 20C. It should read 0 then.

Also, there is a strong possibility that your fermentation is still going since you have a fair amount of krausen still. Have you had stable reading for 3 days in a row?

How long since you pitched the yeast?

 

[TheDudeAbides]

Thanks for the replies.
Manticle: not sure if the yeast is fresh, but it is kept in the fridge at the shop, and as soon as I get it home, I pop it in the fridge until I pitch it. I will look into the things you suggested.
RelaxedBrewer: a busted hydrometer was the first thing I thought. It's reading fine. I pitched the yeast on the 31st December and have had the same SG for the last two days. Do you think I should leave it until the krausen dies down, or is that irrelevant?

Cheers for the help.