Letter head not printed in pdf

Some modules like quotation and purchase order are not printing letter head.

We have not made any changes to any print format or letter head, but these modules started not printing letter head…

Upon inspection, we realized the print format is not printing the heading section:

Print format are legacy print formats (not made by print designer).

In short, some modules are not printing properly.

Any insights would be helpful.

Following apps are installed:

erpnext 15.20.6
frappe 15.23.0
hrms 15.19.0
payments 0.0.1

wkhtmltopdf 0.12.6.1 (with patched qt)

You may need to update the wkhtmltopdf

it is already the latest v0.12.6.1