Redactor/HTMLPurifier won't allow entry update CraftCMS

Question

I'm fairly new to all this.... can you guys help me work out what is wrong here?

Most of my site is fine. When I try to edit a Redactor Field however, I get the error

Class 'HTMLPurifier_AttrDef_HTML_ContentEditable' not found

If I press "Save" it just gives me a craft styled INTERNAL SERVER ERROR page

Stack Trace from craft's web.log file... This happens when trying to save an entry on my production server (DigitalOcean, RunCloud). Works fine on my development stack (Lando)

2022-10-11 16:51:02 [-][1][u3gqq1j4ho4jmi8dnbbdtm0e9u][error][Error] Error: Class 'HTMLPurifier_AttrDef_HTML_ContentEditable' not found in /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/ezyang/htmlpurifier/library/HTMLPurifier/AttrTypes.php:44
Stack trace:
#0 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/ezyang/htmlpurifier/library/HTMLPurifier/HTMLModuleManager.php(77): HTMLPurifier_AttrTypes->__construct()
#1 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/ezyang/htmlpurifier/library/HTMLPurifier/HTMLDefinition.php(187): HTMLPurifier_HTMLModuleManager->__construct()
#2 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/ezyang/htmlpurifier/library/HTMLPurifier/Config.php(630): HTMLPurifier_HTMLDefinition->__construct()
#3 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/ezyang/htmlpurifier/library/HTMLPurifier/Config.php(611): HTMLPurifier_Config->initDefinition()
#4 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/craftcms/cms/src/helpers/HtmlPurifier.php(51): HTMLPurifier_Config->getDefinition()
#5 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/yiisoft/yii2/helpers/BaseHtmlPurifier.php(53): craft\helpers\HtmlPurifier::configure()
#6 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/craftcms/html-field/src/HtmlField.php(193): yii\helpers\BaseHtmlPurifier::process()
#7 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/craftcms/redactor/src/Field.php(506): craft\htmlfield\HtmlField->serializeValue()
#8 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/craftcms/cms/src/base/Element.php(2150): craft\redactor\Field->serializeValue()
#9 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/yiisoft/yii2/validators/InlineValidator.php(84): craft\base\Element->validateCustomFieldContentSize()
#10 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/yiisoft/yii2/validators/Validator.php(261): yii\validators\InlineValidator->validateAttribute()
#11 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/yiisoft/yii2/base/Model.php(367): yii\validators\Validator->validateAttributes()
#12 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/craftcms/cms/src/services/Elements.php(2562): yii\base\Model->validate()
#13 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/craftcms/cms/src/services/Elements.php(785): craft\services\Elements->_saveElementInternal()
#14 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/craftcms/cms/src/controllers/EntriesController.php(407): craft\services\Elements->saveElement()
#15 [internal function]: craft\controllers\EntriesController->actionSaveEntry()
#16 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/yiisoft/yii2/base/InlineAction.php(57): call_user_func_array()
#17 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/yiisoft/yii2/base/Controller.php(178): yii\base\InlineAction->runWithParams()
#18 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/yiisoft/yii2/base/Module.php(552): yii\base\Controller->runAction()
#19 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/craftcms/cms/src/web/Application.php(293): yii\base\Module->runAction()
#20 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/craftcms/cms/src/web/Application.php(602): craft\web\Application->runAction()
#21 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/craftcms/cms/src/web/Application.php(272): craft\web\Application->_processActionRequest()
#22 /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/yiisoft/yii2/base/Application.php(384): craft\web\Application->handleRequest()
#23 /home/teraukura/webapps/Te_Raukura/Te-Raukura/web/index.php(21): yii\base\Application->run()
#24 {main}

Also get this in the log sometimes?

[12-Oct-2022 15:38:55 Pacific/Auckland] PHP Fatal error: Trait 'GuzzleHttp\ClientTrait' not found in /home/teraukura/webapps/Te_Raukura/Te-Raukura/vendor/guzzlehttp/guzzle/src/Client.php on line 17