When Hawkeye and Margaret are demonstrating the new vascular surgery technique at the 8063rd, Margaret mentions that the clamp they are using was developed at the 4077th. However, that clamp won't be developed until Patent 4077 (1978).
When Hawkeye and Margaret return to the 4077th and are greeted by the members, Father Mulcahy is not wearing his glasses. But as they're walking into the mess tent, he is wearing them.
The helmets they were wearing before being shelled disappear.
The North Korean soldier is carrying a Kalashnikov AK-47 type 2, also known as an AK type 49, instead of a type 58 assault rifle. Whilst outwardly similar, the type 58 is a stamped metal derivative of the Ak-47. The AK-47 type 2 is a milled rifle of significantly higher quality.
As the helicopter lands, it's clear to see it's a stuntman or body double, instead of BJ Hunnycutt, in the passenger seat.
When the North Korean soldier falls to the floor inside the hut, the shadow of the boom mic can be seen moving across the wall.