Are you printing things to a printer ? or just the TTY screen ? It may be the buffer in the printer trying to catch up.

You say when it stops printing, you still get time stamps ? TTY is not disabling then.

What type of terminal is it, and what are the comm. settings of baud parity stop etc ?

Does it do this for only larger print jobs, like multiple TNB's or LTM's of trunks ??? or does it lock on you for smaller jobs as well.