Radio buttons built same way behaving differently

Hello all, 

I'm wondering if anyone knows why radio button groups (built in InDesign and then interactive-exported to Acrobat) are behaving differently even though they were built/named/grouped the same way? 

Some of them (group1 and group2 for example) tab through to each radio button in a group and some of them (group3 and group6 on the next page for example) tab to the first radio button in each group (the way a radio group should work ... where you would arrow to your choice, etc.). This randomly happens across my document for 120 or so radio groups. There is no rhyme or reason.   

Why would that happen?

P.S. I'm familiar with the CommonLook suggestion to use JavaScript (example below) to hard code mutually exclusive radio buttons "in a group," (<-- not really) but with a different name. I would like to avoid that route for two reasons: Screen-reader users in my organization say the same-name-groups with unique radio button choice values work better for them, and also becuase I have 120+ radio groups and that is A LOT of remediation work at this point. 
 

var A = this.getField("RadioButton1");

var B = this.getField("RadioButton2");

var C = this.getField("RadioButton3");

var D = this.getField("RadioButton4");

if (A.value == "Individual"){

B.value = "Off";

C.value = "Off";

D.value = "Off";