Upgrade v12 to v13 (Customized Form Issues)

After successful upgrade of existing installation I’m getting an issue with Customized Form fields. Note, these fields exist in the parent forms as Date (Batch) and Text fields Newly added in (Item). The problems are below.

FORM: Purchase Receipt Items
v12 – added 3 new fields being populated from Items and Batch:
1. Added Storage Temp Range with:
a. Type - Data
b. Options - Item
c. Fetch From - item_code.storage_temp_range
2. Added Waste Class with:
a. Type - Data
b. Options - Item
c. Fetch From - item_code.storage_temp_range
3. Added Expiry Date with:
a. Type - Data
b. Options - Batch
c. Fetch From - batch_no.expiry_date

All above fields in v12 worked perfectly.
However, once I migrated to v13 issues arose with the above fields, i.e.:
1. Storage Temp Range
a. I receive an error indicating that the Field is an invalid Data field
b. Only options for Data field are;
i. Email
ii. Name
iii. Phone
2. The same error occurs with the other fields

I then tried to delete the fields in the above form and re-create them with different data types:
1. Added Storage Temp Range with:
a. Type - Read Only
b. Options -
c. Fetch From -
2. Added Waste Class with:
a. Type - Read Only
b. Options -
c. Fetch From -
3. Added Expiry Date with:
a. Type - Date
b. Options - Batch
c. Fetch From - batch_no.expiry_date
The above worked and returned the correct data from the other forms. However, if functional difference exists in all forms there will need to be quite a bit of work to re-factor existing forms.

My questions then:
1 Is this a bug that needs to be fixed before I move production data to the new environment?
3. If the fields need to be modded from v12, is there a routine that can hunt for the differences and automatically change them to the correct data types?
4. Are we left to our own to fix individual forms?

Thanks