vlookup returns 0 and 1900 date in range of cells when only 1 has been filled in.

[GodzFire]

I have the following setup: Each of my cells does a vlookup for a matching record in either of 2 other source data tabs. If it finds a match, it puts them in the associated cells. When the Date Replaced cell is filled in with a date, an 'x' is entered into the associated S column, via a conditional formatting formula.

Discovered problem: If someone enters just 1-3 of the 4 pieces of information in one of the 2 other source data tabs but leave the others blank, Excel will still fill the remaining ones left, but with either 0s for text and 1900 for date, which then triggers the conditional formatting and puts the 'x' in column S when it shouldn't. I'm not sure how to make it so the other ones don't trigger / stay blank until something is actually inputted into them.

Here are my forumulas. Also if there is a better formula to accomplish what I am trying to do, I am totally open.
O: =IFERROR(VLOOKUP(C144,FYInv!L:O,3,FALSE),VLOOKUP(C144,'FY18 Ref'!L:O,3,FALSE))
P: =IFERROR(VLOOKUP(C144,FYInv!L:O,1,FALSE),VLOOKUP(C144,'FY18 Ref'!L:O,1,FALSE))
Q: =IFERROR(VLOOKUP(C144,FYInv!L:O,2,FALSE),VLOOKUP(C144,'FY18 Ref'!L:O,2,FALSE))
R: =IFERROR(VLOOKUP(C144,FYInv!L:O,4,FALSE),VLOOKUP(C144,'FY18 Ref'!L:O,4,FALSE))
S: =IF(ISNUMBER(R144),"x","")

 

[etaf]

=IF(IFERROR(VLOOKUP(C144,FYInv!L:O,3,FALSE),iferror(VLOOKUP(C144,'FY18 Ref'!L:O,3,FALSE),""))=0,"",
IFERROR(VLOOKUP(C144,FYInv!L:O,3,FALSE),iferror(VLOOKUP(C144,'FY18 Ref'!L:O,3,FALSE),"")))

 

[GodzFire]

Thanks for sticking with me etaf, that did it! Thanks for everything!