The Garand had problems with exterior debris and water washing the lubricant out of the rifle. It did have significantly more development time than the Johnson, which would have helped it be a better rifle.
Clip from:
https://firearmusernetwork.com/2015/03/05/united-states-rifle-caliber-30-m1-m1-garand-unreliable/ that references a Time magazine article from 1941 (that’s behind a paywall that I can’t access)
“– The rifles were doused in mud “of light consistency.” Results: “The M-1903 [Springfield] rifle can be operated. However, the bolt became harder to operate as the test progressed. . . . The M-1 [Garand] rifles would not function and the longer an attempt was made to operate the bolt by hand the harder it became to open.”
– The board assumed “that troops have landed through light surf [as Marines must often do] and that rifles were dropped or dragged over wet sand in reaching cover on the beach.” The rifles were exposed to saltwater spray (but not actually soaked in water), dropped in wet sand. Results: the Springfields fired “in the normal manner.” But “the bolts on the two [Garands] could not be opened by hand after the first and second shots respectively. The firer had to stand up and use his foot against the operating handle in order to open the actions. Both [Garand] rifles . . . failed this test.”
– The board assumed “that troops have landed through heavy surf sufficient to break completely over men and equipment, and immediately engage in combat on a sandy beach.” Results: both Garands failed to operate as semi-automatic rifles (i.e., reload automatically after each round). One failed completely and the firer had to hammer the bolt with a mallet; “the other operated by hand with extreme difficulty. …” The Springfields continued to work, with slight difficulty. On these salt water tests, the Garand was rated last, the Springfield first.”
BSW