Today I got this error while importing ST-A/PI package.
There is a very good solution here: http://scn.sap.com/thread/1902597
But this time I decided to review the file /usr/sap/trans/buffer/TST in AL11, which
is responsible for the STMS buffer.
I noticed a single ~ symbol alone on a line, somewhere in the middle of the file.
Deleted it (along with the whole line) and it’s OK now, and the buffer stays filled.
I needed it because I have many transports queued.
So you have to search for a extraordinary line.
Tip: don’t look at the lines beginning with #, I think STMS/tp ignores them…
Cheers & Good Luck