Slow loading Apple Mail on iMac Pro

Not sure when this started but seems that there has been a change to Apple Mail which is making it very slow to load, especially when there are attachments added. Once an attachment is selected, it can take up to 30 seconds to release the cursor to continue with the email. This does not apply to attachments that are not displayed in the mail such as xls file or PDFs with multiple pages where there is just an icon displayed. Does anyone know if something was changed? Does anyone else have the same issue? Can anything be done about it as it makes sending email very slow. Does not apply to emails from iPhone or iPad (iOS systems). Problem is from my iMac Pro Sonoma 14.5.