>Not being a war expert I have no idea what these numerous problems were. What were they?<

From memory the problems were those of strategic deployability, with the Abrams units requiring greater numbers of personnel and MT support, operating, withunits requiring significant climatic conditions modifications in-theatre, and some component and sub-system failure for same reasons. There were cases of 'cannibalism' with the Army stripping most of the M1s that were delivered to the USMC due to in-theatre shortage of spares. Performance in some terrains left much to be desired; M1s had been tested in sand terrain which I later found out to be a lot on a General Dynamics property, and not something that would have been expected or for that matter unexpected, in combat operations.

Its all 'water under the bridge now' since there were several projects to upgrade the M1A1s after the 1st Gulf War, including to complete the re-arming of the US-based tanks with the 120mm guns.