A series of injuries badly affected Yapton, for whom Gary Aldridge headed home from Scott Hunter's cross to make it 1-1 at half-time.
Both Yapton centre-backs were hurt in the first half, left the field and were substituted. Others were afflicted after the break but had to carry on as there were no more subs.
Eventually, one of them hobbled off, leaving Yapton to battle with 10 men. Sesley rattled in three more with Curtis Booker on target for the visitors.
In Division 3S Yapton Reserves lost 4-2 away to Flansham Park Rangers. After trailing 2-0, Paul Middleton, with a fine volley, and Luke Yates equalised, but Rangers hit back with two more in quick succession.
Yapton 3rd gave away a late goal to fall 2-1 away to Fittleworth Reserves in Divison 3C. Brandon Terry headed home Josh Dean's long throw for Yapton.