What is the role of 在 in the sentence 当我有错误在帮我纠正就行了 Ｉ understand 当 serves as the start of &quot;When xyz, then abc&quot; or &quot;當 。。。时，xyz&quot; but what exactly is 在 doing in this sentence?

当我有错误【在】帮我纠正就行了。

Couldn't you just say:
当我有错误【时】帮我纠正行了。
It may be a mistake. It should be 当我有错误再帮我纠正就行了 or the complete version 当我有错误的时候再帮我纠正就行了 .
There is no relationship between 再 and 时 . There will always be a 时 in the meaning of this sentence even though you can omit it.
Because  of 就行了 ; there will always be a 再 in the meaning of this sentence.
After you remove 就行了. 再 makes this sentence sounds like &quot;not now; correct me untill I made a mistake&quot;. If you remove 再,  this sentence will become a imperative sentence like an order.