Walmart cheapies pregnancy test

For those of you who use the equate one dollar pregnancy test from Walmart, how often do you see evap lines. So I tested and with in four minutes, test looked negative. 15 min later I saw a line so I thought it’s an evap line because it was read outside the time window and maybe this test packet has an issue. So the next morning I test and same thing except the line showed after ten min. I’ve used these before with my previous pregnancy’s and I never saw evap lines after the fact. Could it be this batch of test is doing this? Any thoughts?