Add routine that caches account balances. Add it to the /flush routine as well.

app/Console/Commands/Correction/CorrectBalanceAmounts.php

@@ -0,0 +1,49 @@
+<?php
+
+namespace FireflyIII\Console\Commands\Correction;
+
+use DB;
+use FireflyIII\Models\AccountBalance;
+use FireflyIII\Models\Transaction;
+use Illuminate\Console\Command;
+use stdClass;
+
+/**
+ * Class CorrectionSkeleton
+ * TODO DONT FORGET TO ADD THIS TO THE DOCKER BUILD
+ */
+class CorrectBalanceAmounts extends Command
+{
+    protected $description = 'Recalculate all account balance amounts';
+
+    protected $signature = 'firefly-iii:correct-balance-amounts';
+
+    /**
+     * @return int
+     */
+    public function handle(): int
+    {
+        $this->correctBalanceAmounts();
+
+
+        return 0;
+    }
+
+    private function correctBalanceAmounts(): void
+    {
+        $result = Transaction
+            ::groupBy(['account_id', 'transaction_currency_id'])
+            ->get(['account_id', 'transaction_currency_id', DB::raw('SUM(amount) as amount_sum')]);
+        /** @var stdClass $entry */
+        foreach ($result as $entry) {
+            $account  = (int) $entry->account_id;
+            $currency = (int) $entry->transaction_currency_id;
+            $sum      = $entry->amount_sum;
+
+            AccountBalance::updateOrCreate(
+                ['account_id' => $account, 'transaction_currency_id' => $currency],
+                ['balance' => $sum]
+            );
+        }
+    }
+}

app/Console/Commands/Correction/CorrectDatabase.php

@@ -74,6 +74,7 @@ class CorrectDatabase extends Command
             'firefly-iii:unify-group-accounts',
             'firefly-iii:trigger-credit-recalculation',
             'firefly-iii:migrate-preferences',
+            'firefly-iii:correct-balance-amounts',
         ];
         foreach ($commands as $command) {
             $this->friendlyLine(sprintf('Now executing command "%s"', $command));