https://www.odoo.com/nl_NL/forum/help-1/question/it-is-not-possible-to-unreserve-more-products-of-than-you-have-in-stock-138783#:~:text=It happens because the reserved

1.debug mode

2.technical/server actions

3.create

4.action name: e.g. fix unreserved qty

5.model: ir.actions.server

6.action to do: "execute python code"

7.copy/paste the fix underneath the pre-existing code

8."save" 

quants = env["stock.quant"].search([])

move_line_ids = []

warning = ""

for quant in quants:

    move_lines = env["stock.move.line"].search(

        [

            ("product_id", "=", quant.product_id.id),

            ("location_id", "=", quant.location_id.id),

            ("lot_id", "=", quant.lot_id.id),

            ("package_id", "=", quant.package_id.id),

            ("owner_id", "=", quant.owner_id.id),

            ("product_qty", "!=", 0),

        ]

    )

    move_line_ids += move_lines.ids

    reserved_on_move_lines = sum(move_lines.mapped("product_qty"))

    move_line_str = str.join(

        ", ", [str(move_line_id) for move_line_id in move_lines.ids]

    )

    if quant.location_id.should_bypass_reservation():

        # If a quant is in a location that should bypass the reservation, its `reserved_quantity` field

        # should be 0.

        if quant.reserved_quantity != 0:

            quant.write({"reserved_quantity": 0})

    else:

        # If a quant is in a reservable location, its `reserved_quantity` should be exactly the sum

        # of the `product_qty` of all the partially_available / assigned move lines with the same

        # characteristics.

        if quant.reserved_quantity == 0:

            if move_lines:

                move_lines.with_context(bypass_reservation_update=True).write(

                    {"product_uom_qty": 0}

                )

        elif quant.reserved_quantity < 0:

            quant.write({"reserved_quantity": 0})

            if move_lines:

                move_lines.with_context(bypass_reservation_update=True).write(

                    {"product_uom_qty": 0}

                )

        else:

            if reserved_on_move_lines != quant.reserved_quantity:

                move_lines.with_context(bypass_reservation_update=True).write(

                    {"product_uom_qty": 0}

                )

                quant.write({"reserved_quantity": 0})

            else:

                if any(move_line.product_qty < 0 for move_line in move_lines):

                    move_lines.with_context(bypass_reservation_update=True).write(

                        {"product_uom_qty": 0}

                    )

                    quant.write({"reserved_quantity": 0})

move_lines = env["stock.move.line"].search(

    [

        ("product_id.type", "=", "product"),

        ("product_qty", "!=", 0),

        ("id", "not in", move_line_ids),

    ]

)

move_lines_to_unreserve = []

for move_line in move_lines:

    if not move_line.location_id.should_bypass_reservation():

        move_lines_to_unreserve.append(move_line.id)

if len(move_lines_to_unreserve) > 1:

    env.cr.execute(

        """ 

            UPDATE stock_move_line SET product_uom_qty = 0, product_qty = 0 WHERE id in %s ;

        """

        % (tuple(move_lines_to_unreserve),)

    )

elif len(move_lines_to_unreserve) == 1:

    env.cr.execute(

        """ 

        UPDATE stock_move_line SET product_uom_qty = 0, product_qty = 0 WHERE id = %s ;

        """

        % (move_lines_to_unreserve[0])

    )