After transferring website - PHP Fatal error: Allowed memory size of 41943040 bytes exhausted (tried to allocate 32768 bytes) [duplicate]

I am transferring website from one host to another.A very strange error occurred that I haven't seen before.

PHP Fatal error: Allowed memory size of 41943040 bytes exhausted (tried to allocate 32768 bytes)

I thought that this was a wp memory limit issue so I added this to my wp-config.php file

define( 'WP_MEMORY_LIMIT', '8096M' );define( 'WP_MAX_MEMORY_LIMIT', '8096M' );

But the website keeps returning error 500, and this error in my error log.

Anyone any ideas?