Here is a quick search I did....
Hebrews 12:15 (AMP)
Exercise foresight and be on the watch to look [after one another], to see that no one falls back from and fails to secure God's grace (His unmerited favor and spiritual blessing), in order that no root of resentment (rancor, bitterness, or hatred) shoots forth and causes trouble and bitter torment, and the many become contaminated and defiled by it--
JFB
lest any ... fall — Greek, “lest any (namely, through sloth in running) failing,” or “falling short of the grace of God ... trouble you.” The image is taken from a company of travelers, one of whom lags behind, and so never reaches the end of the long and laborious journey [Chrysostom].
VWS
Fail of
Rend. “fall back from,” implying a previous attainment. The present participle marks something in progress: “lest any one be falling back.”
Wuest
The word "fail" is hustereo "to come late or too tardily." In Heb_4:1 it means "to be left behind in the race and so fail to reach the goal, to fall short of the end." It is used here with the preposition apo which means "off, away from," and means "to fall back from," implying a previous attainment. The participle is in the present tense and thus speaks of something in progress. The translation is "lest any one be falling. ....
Cambridge
lest any man fail of the grace of God] Lit. “whether there be any man who is falling short of,” or possibly “falling back from the grace of God.” ....