Ethminer stopped working for my 4gb cards this morning as well.  And my rigs with 8gb cards are still working fine. 

I run ubuntu 18.04 no custom OS.  And Claymore v15 still works on the 4gb cards.

Must be some code issue with how ethminer handles buffer allocation

cl 16:56:55 cl-1     Build info success:
cl 16:56:55 cl-1     Creating light cache buffer, size: 60.00 MB
cl 16:56:55 cl-1     Creating DAG buffer, size: 3.75 GB, free: 190.37 MB
 X 16:56:55 cl-1     Creating DAG buffer failed: clCreateBuffer: CL_INVALID_BUFFER_SIZE (-61)
SIGSEGV encountered ...


I bet ethOS runs ethminer as well

Thanks for sharing your mining operation build out, its very impressive.

Where did you source your large intake vents?  Do you run any type of dust filtration or is it just mesh screening for bugs?

I placed an order June 29th and also have not received any tracking info yet.  I have been ordering from them since March and they are usually pretty good about replying to my emails when checking on order status and will even upgrade shipping to over night when there is an abnormally long delay. 

They show a 4 day minimum backlog on the home page

And could be they got some huge orders that take precedence over us small guys.