Parameterize Object and looping through skips some numbers

Hi if I paramterize my object and loop through with said code, it does not actually check/click all checkboxes

(1…6).each
{
WebUI.check(findTestObject(‘’, [(‘index’) : it]))
}

it check/clicks 1, 3,4 and 6 … it skips out on 2 and 5

if I change it to (2…6) it check/clicks 2, 4, 6 and skips out on 3 and 5