iPad Air 5th generation fillable PDF saving issues

my husband is trying to save changes made on a fillable PDF form on his iPad Air but these changes won’t save. It will save some of the text that he enters but any tick box entries and much of the typed in entries are lost.

we saved the fillable PDF forms in the files folder and have tried using adobe acrobat reader and acrobat reader pro apps but have had no luck. Anyone have any ideas on how we can make this work?