Weird situation with alerts through telegram (Alert message is not sent, but "ok" message sent well)

Since I updated to v6.1.3, alerts through telegram are not working as expected, by email works as always.

Alerting message is not sent, or at least is not arriving. But resolve message is sent perfectly.

I made a curl from the grafana host and works fine. Any idea?

From the log, but resolve message has photo too:

t=2019-04-17T04:59:07+0000 lvl=info msg="Sending telegram notification" logger=alerting.notifier.telegram chat_id=-11111111 bot_token=1111111111:22222222222222222222222 apiAction=sendPhoto
t=2019-04-17T04:59:07+0000 lvl=eror msg="Failed to send webhook" logger=alerting.notifier.telegram error="Post read tcp> read: connection reset by peer" webhook="Telegram Alerts"
t=2019-04-17T04:59:07+0000 lvl=eror msg="failed to send notification" logger=alerting.notifier uid=000000001 error="Post read tcp> read: connection reset by peer"