Remove EncodeUTF8 infavour of using attribute casting only. The implementation of EncodeUTF8 was not correct, essentially removing any previous casting causing issues when saving a record.

app/Casts/UTF8StringOrNull.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace App\Casts;
+
+use Illuminate\Contracts\Database\Eloquent\CastsAttributes;
+use Illuminate\Database\Eloquent\Model;
+
+class UTF8StringOrNull implements CastsAttributes
+{
+    /**
+     * Cast the given value.
+     *
+     * @param  array<string, mixed>  $attributes
+     */
+    public function get(Model $model,string $key,mixed $value,array $attributes): ?string
+    {
+        return $value ? utf8_decode($value) : NULL;
+    }
+
+    /**
+     * Prepare the given value for storage.
+     *
+     * @param  array<string, mixed>  $attributes
+     */
+    public function set(Model $model,string $key,mixed $value,array $attributes): ?string
+    {
+        return $value ? utf8_encode($value) : NULL;
+    }
+}