Check 'show controller e1 0/0' (same for e1 0/1) and see if there is more information on errors type. If you see many line code violation, chances are that you have clock issue. You can see meaning of other type of errors in the following document:
Also, try extended ping to remote end with verification of replies enabled and pattern for the test 0x0000 (one or two packets won't matter, send few thousand pings, ).
If you suspect clock issue and you manage the router on the other end of the link, be sure that one router is configured for 'clock source internal' and the other 'clock source line' (default). If remote router is operated by other people contact them and agree who should provide clock (usually provider).
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...