Your message prompted me to check logs, and on one relay I see the following:
Similar thing for me:
Jul 19 00:08:27.000 [notice] Circuit handshake stats since last time: 3571/3571 TAP, 41180/41180 NTor. Jul 19 06:08:27.000 [notice] Circuit handshake stats since last time: 2054/2054 TAP, 29181/29181 NTor. Jul 19 12:08:28.000 [notice] Circuit handshake stats since last time: 2773/2773 TAP, 26497/26497 NTor. Jul 19 18:08:28.000 [notice] Circuit handshake stats since last time: 3970/3970 TAP, 31344/31344 NTor. Jul 20 00:08:28.000 [notice] Circuit handshake stats since last time: 4096/4096 TAP, 41730/41730 NTor. Jul 20 06:08:28.000 [notice] Circuit handshake stats since last time: 18285/18285 TAP, 54102/54102 NTor. Jul 20 12:08:28.000 [notice] Circuit handshake stats since last time: 61136/61386 TAP, 378196/378339 NTor. Jul 20 18:08:29.000 [notice] Circuit handshake stats since last time: 73297/73688 TAP, 566708/566892 NTor. Jul 21 00:08:29.000 [notice] Circuit handshake stats since last time: 67165/67830 TAP, 572685/572851 NTor. Jul 21 06:08:29.000 [notice] Circuit handshake stats since last time: 31988/32138 TAP, 521455/521536 NTor. Jul 21 12:08:29.000 [notice] Circuit handshake stats since last time: 5523/5523 TAP, 222378/222432 NTor.
Also there are too much "[warn] assign_to_cpuworker failed. Ignoring." lines in the logs.
-- Vort