After choosing a match to spectate from the Watch menu, over the course of spectating the match the client begins to degrade and eventually disconnects with the following console output (numbers differ between matches but the output is otherwise the same):
[HLTV Broadcast] 5827.42. Playcast cannot retrieve fragment 3231, retrying [HLTV Broadcast] 102000. Stream State Delta Frames -> Stop, fragment 3228 [Client] CL: Disconnecting from server: NETWORK_DISCONNECT_HLTVSTOP [HLTV Broadcast] Playcast Canceling Fragment 3231 [HLTV Broadcast] Playcast Canceling Fragment...
Here is the similar thread that's a bit more active, same issue here
you can f7 type "disconnect" in order to not have to restart the process