Put data from one specific cell to another BETWEEN two sheets

I have 3 sheets: USERS, ITEMS, INVENTORY.

USERS include two categories: ADMINS and REG_USERS.

Let’s say im an ADMIN and i want to «give» to a REG_USER one of ITEMS.

By first action I grab REG_USER’s INVENTORY RowID and set it to special column in USERS sheet, in my own row, then Link to screen ITEMS.

By the second action i want to tap on a specific item in the list > set it’s name to REG_USER’s INVENTORY > Go back. So im doing the following:

  1. Put REG_USER’s INVENTORY RowID (grabbed earlier) from my own temporary cell to special «Sharing» column in ITEMS by tapping the necessary item in list.

  2. In ITEMS sheet i already have a relation column «Rel_Inventory» which set as «Sharing» to «INVENTORY > RowID». This relation makes connection between specific ITEMS row and specific INVENTORY row, so while «Sharing» column is empty, this relation doesn’t work. But it starts working right at the moment of tapping.

  3. Set columns in «Rel_Inventory»: Shared_Item — Item_name.

When testing this from editor on desktop it works. But when im trying to do the same on my mobile it doesn’t work — «Item_name» doesn’t appear in «Shared_Item». What’s wrong? May be some kind of connection lag? I’m confused. Please, any thoughts.