That's not enough errors, it takes massive errors to cause a circuit to slip. I would think your timing option is incorrect rather than a bad card.
is there any way that the something down stream could be causing the slips?
No. I worked many years in a T-1 center and never once saw anything but CPE equipment cause slips. It's simple the timing source (Telco) can't be out of time. The same thing can happen CO to CO if the slave end is optioned incorrectly.
