Running drush updb - get The process has been signaled with signal "11"

Also had this issue, on Pantheon:

❯ terminus drush site-name.dev updb
[warning] This environment is in read-only Git mode. If you want to make changes to the codebase of this site (e.g. updating modules or plugins), you will need to toggle into read/write SFTP mode first.
In Process.php line 441:
The process has been signaled with signal "11". [notice] Command: saint-pauls-school.dev -- drush updb [Exit: 1]
[error]
~ 16s

I had seen the same issue in Pantheon dashboard 2 days earlier, but the DB update seemed to have run, so did not worry too much about it.

There was one module on the site that was saying it was "not supported" - Smart Date 3.6.1
I updated that module and that seemed to fix it.
I am not 100% that was the fix but posting here in case it gives others ideas.

To fix this issue on Pantheon, change the following in your composer.json:

Set

"allow-plugins": {
    "dealerdirect/phpcodesniffer-composer-installer": false
}