Concat function fails for inexplicable reason

Hello all,

While applying concat function to a bunch of hidden fields, parsing the last field throws an error. I cannot figure out why! The schema is here.

Field play1 is a concatenation of a bunch of hidden fields, defined earlier. In the concatenated form, the play1 should look like (1/2/False/0/5). However, during preview, I am told that the last field (‘5’ here) cannot be produced. Here is the screenshot:

As is obvious, first four ‘slash’-separated fields have been concatenated alright. Mockaroo’s unhappiness about the last field is evident from the message. BTW, the last field in the schema, doesn’t even have a ’ __play1 ’ prefix (it is named __takenToAnswerAtFE). The message is confusing me.
Moreover, the next field in the scheme - pause1 - is a Custome List (Sequential). But the error message hints at something completely different.

Could someone give me a helping hand? I don’t know Ruby, just in case a lack there is causing me the distress.

Update: I have tested the behaviour. It is confusing for sure. If I begin with one field and “/” - and then progressively add more fields - it works till the last field ( __takenToAnswerAtFE ) is added. That’s when it throws that error I have mentioned earlier.

– Nirmalya