diff --git a/shop/lib/actions/companies.ts b/shop/lib/actions/companies.ts
index 7aab64b..92dcc4d 100644
--- a/shop/lib/actions/companies.ts
+++ b/shop/lib/actions/companies.ts
@@ -286,34 +286,49 @@ export async function syncCustomersFromLicServer() {
   // 2. Fetch customers for each company
   for (const company of companies) {
     try {
-      const res = await fetch(`${cfg.base_url}/api-v1/partners/${company.id}/customers?pageSize=1000`, {
-        headers: { 'X-Api-Key': cfg.api_key, 'Accept': 'application/json' },
-        signal: AbortSignal.timeout(10_000),
-      })
+      // Workaround for LicServer crash on null/empty search parameter:
+      // We query using common vowels/umlauts in parallel and de-duplicate locally.
+      const searchChars = ['a', 'e', 'i', 'o', 'u', 'ä', 'ö', 'ü', 'y']
+      const customerMap = new Map<string, any>()
 
-      if (res.ok) {
-        const result = await res.json()
-        const customers = result.items || []
+      await Promise.all(
+        searchChars.map(async char => {
+          try {
+            const res = await fetch(`${cfg.base_url}/api-v1/partners/${company.id}/customers?pageSize=1000&search=${encodeURIComponent(char)}`, {
+              headers: { 'X-Api-Key': cfg.api_key!, 'Accept': 'application/json' },
+              signal: AbortSignal.timeout(10_000),
+            })
+            if (res.ok) {
+              const result = await res.json()
+              const items = result.items || []
+              for (const c of items) {
+                customerMap.set(c.id, c)
+              }
+            }
+          } catch (e: any) {
+            console.error(`[sync-customers] Error fetching with search=${char} for partner ${company.id}:`, e.message || e)
+          }
+        })
+      )
 
-        for (const c of customers) {
-          const streetCombined = [c.street, c.houseNumber, c.houseNumberAddon]
-            .filter(Boolean)
-            .map(s => s.trim())
-            .join(' ')
+      const customers = Array.from(customerMap.values())
 
-          allUpsertRows.push({
-            id: c.id,
-            partner_id: company.id,
-            company_name: c.name || 'Unbenannt',
-            street: streetCombined || null,
-            zip: c.zipCode || null,
-            city: c.city || null,
-            email: c.email || null,
-            is_anonymized: false,
-          })
-        }
-      } else {
-        console.warn(`[sync-customers] Skipping partner ${company.id} due to API status: ${res.status}`)
+      for (const c of customers) {
+        const streetCombined = [c.street, c.houseNumber, c.houseNumberAddon]
+          .filter(Boolean)
+          .map(s => s.trim())
+          .join(' ')
+
+        allUpsertRows.push({
+          id: c.id,
+          partner_id: company.id,
+          company_name: c.name || 'Unbenannt',
+          street: streetCombined || null,
+          zip: c.zipCode || null,
+          city: c.city || null,
+          email: c.email || null,
+          is_anonymized: false,
+        })
       }
     } catch (e: any) {
       console.error(`[sync-customers] Error fetching customers for partner ${company.id}:`, e.message || e)