Global Sell Price is not applied when credited quantity is changed - 7.00.175
Creating a credit note based on on a sales order by default, uses the current pricing applicable to the customer for the lines being credited. To retain the original invoiced price, enable the plugin Sales Order Credit Note Fix Price which sets the fix price flag of each line is set to ensure changes to quantities do not recalculate the price.
Adding news lines to the credit notes applies current pricing
Note: In 7.02.01 where a credit note is based on a sales order, the same prices are applied even if the quantity being credited is changed
Step-by-step guide
To enable the plugin
System Settings > Plugin Maintenance > Plugins
Load the search windows and select the plugin 'Sales Order Credit Note Fix Price'
Tick Enabled check box and save
Log out and back in again to compile the plugin
Credit notes based on a sales order will apply original pricing from the sales order.