I expect this is actually another instance of one of the earlier bug reports but anyway...
If the atoms are ordered: CC=C(C(O)=O)CP+=O
one gets:
InChI=1S/C5H7O4P/c1-2-4(5(6)7)3-10(8)9/h2H,3H2,1H3,(H-,6,7,8,9)/p+1
but if they are ordered: CC=C(CP+=O)C(O)=O
one gets:
InChI=1S/C5H6O4P/c1-2-4(5(6)7)3-10(8)9/h2H,3H2,1H3/q-1/p+2