Long loading times in sharepoint "Add new item" dropdown list for lookup column

Hi everyone, I currently have a sharepoint list which includes a lookup column, whereby a scanner scans in a [code] into the "Add new item" form, and it will return a [name] in a seperate column in the list. There are currently about 1K - 2K items in the lookup list.

When i press the lookup column, it is able to generate the full list without issue.

However, if i try to search for the exact [code], the search/filter function in the dropdown list is not able to find the exact code (see below image). Previously there wasn't any issue with this, but it seemed to appear after the new UI update of sharepoint list.

If edit using grid view, the list is able to search/filter without any issues

Does anyone have any potential solution to the long search times when using the "add new item" button/form? Much appreaciated!