no builders available in region - falling back to global scheduling

Question

i see this error in the build logs 
eventually, i see logs around docker image pushing and it is very slow:

image push progress: 419 MB/1.8 GB
image push progress: 428 MB/1.8 GB
image push progress: 438 MB/1.8 GB
image push progress: 447 MB/1.8 GB
image push progress: 456 MB/1.8 GB
image push progress: 466 MB/1.8 GB
image push progress: 475 MB/1.8 GB
image push progress: 485 MB/1.8 GB
image push progress: 494 MB/1.8 GB
image push progress: 504 MB/1.8 GB
image push progress: 513 MB/1.8 GB
image push progress: 522 MB/1.8 GB
image push progress: 532 MB/1.8 GB
image push progress: 541 MB/1.8 GB