Radak on Genesis 24:33:1:
ויישם, כתיב, וכן ויישם בארון (שמות כ"ה) שרש ישם; וקרי ויושם מבנין
הפעל, הושם לפניו לאכול על יד נערי הבית.
, the word is spelled ויישם, “he placed,” although it is read as
vayussam, “it was placed.” We find a similar anomaly in Genesis 50,26
when placing Joseph’s remains in a coffin is reported. The root of the
verb is ישם.
In other words, the Ktiv indicates the active voice, whereas the Kri indicates the passive voice. As Rada"k doesn't explain any "hidden" meaning, and the verse itself mentions no direct subject, one might wonder who did the placement. Thus, the kri seems to correct the grammatical problem, or avoid the vagueness by changing the active to passive.
(FYI, this is a common grammatical technique in English. I learned that when writing always use the active voice. Passive should be used when you don't want to tell your readers who did the action, or that information is irrelevant.)