The cause is most likely the batteries.
Please test the handset with simple 1.5 V batteries, and if it operates normally, the cause is most likely the rechargeable batteries.
IMPORTANT: Do not place the handset with batteries in the base/charging cradle.
Please be sure to use the batteries recommended in your operating instructions.
When you buy new batteries, it is important to charge the batteries once for at least 8-9 hours without interruption, then use the handset normally without charging it until the batteries are completely discharged. It is recommended that you always use the batteries in this way, even later.
You can buy the batteries in our Onlineshop as well as in independent specialist shops.