Images not rendering in livechat

Hello. I am building a bot, using Rasa, with a Rocketchat livechat channel, using docker-compose but have the issue that the images are not showing. In the response, the bot calls the rocketchat api to send a message with an attachment with image_url http(colon)//, but the image does not show in the livechat window, because the URL appears entangled; it appears as http://chat.amxnet.comh_ttp(colon)// (chat(dot)amxnet(dot)com is the Rocket chat server). However, in the administrator view of the chat, the image appears correctly.
FYI, I am using a nginx reverse proxy to serve the site, whithout any explicit configuration. The bot frontend endpoint is served from a routing in Flask (Python). Any help is appreciated