Signatures are inserted with incorrect formatting

My multi-line signatures are in Calibri, few lines are 11pt, few lines are 7pt. When I create a new email, the signature gets inserted with its font changed to Tahoma 12pt with weird line spacing. When in the same window I pick the same signature from the Signatures drop-down, it is inserted with correct format.
When I reply to an email, my Reply signature is correctly inserted in Calibri, but lines that were in 7pt are made 11pt.
Default font for email composing is set to Calibri, 11.

Try to re-create the signature - this usually happens when the signature contains some redundant HTML formatting after the import from Outlook.