fall behind vs fall back

fall behind and fall back both are verbs.

Word	Noun	Adjective	Verb	Adverb
fall behind	No	No	Yes	No
fall back	No	No	Yes	No

As verbs, fall behind and fall back are synonyms defined as:

Other synonyms of fall behind include drop off, recede.

As verbs, fall behind and fall back are synonyms defined as:

fall behind and fall back: hang (back) or fall (behind) in movement, progress, development, etc.

Other synonyms of fall behind include dawdle, lag.

fall behind (verb)	fall back (verb)
retreat	go back to bad behavior
hang (back) or fall (behind) in movement, progress, development, etc.	retreat
	hang (back) or fall (behind) in movement, progress, development, etc.
	fall backwards and down
	move back and away from
	have recourse to