Some of the cloze 1 cards directly reveal answers as shown in the following pic
This issue is likely due to the cloze one-by-one feature enabled on this card. You can correct this by getting the AnKing Note Types Add-on > open the tooltip > scroll down > enable “flip to back automatically”
See if that resolves your issue 
Thank you for your help but the problem still persists.
Even the toggle all button doesn’t work as well for cloze 1 cards, but everything is fine on cloze 2 cards.
Problem solved.
The problem is related to the bolded words which happen to be the cloze.
Just unbold and bold the words will simply fix the issues.