So my Brother SE400 is all of the sudden not filling in the letters it embroiders correctly. Hoping that maybe by the pictures you might be able to tell me what's happening.

Some details: I've successfully used this design before (third picture of red initials is correct). I bought the font off of etsy. The only difference between the red initials and my incomplete black ones is that I changed thread brands from Coats & Clark to Sewology (Coats & Clark is a cheap brand from Walmart, Sewology is supposed to be nicer?). I was using a 4 on the tension dial and also changed to 3 and 2 in trying to fix the problem. 

Thoughts? Surely someone else has had this problem and recovered?

I've posted the front and back (in black), as well as my successful use of the font in red.

 

Hello
Did you think about changing the interior can? It's silly, but sometimes when the latter was in bad wound (just pass much), it can cause such defects.
If you change tenssion, remember to remove and recover your coil wire, I already had the case (especially when using cotton thread) that the new rule does not tenssion if I change the tenssion without stringing new.
It can also happen that resizing the file embroidery can cause defects.

Finally the last thing that I can consseiller is to remove all the son and put the treads.