Why can't we get more than 2 telemetry receivers connected

[RahmaSallm]

We are trying to get telemetry from an ASR1006-X running IOS-XE Version 17.3.5. 
2 telemetry subscription works fine, but when adding a third telemetry subscription it cannot connect to the receiver. It gets stuck in connecting state.

Example;
pe1-sth1#sh telemetry ietf subscription 27 receiver
Telemetry subscription receivers detail:

Subscription ID: **
Address: *************
Port: 6543
Protocol: grpc-tcp
Profile:
Connection: 65535
State: Connecting
Explanation:

pe1-sth1#sh telemetry ietf subscription 23 receiver
Telemetry subscription receivers detail:

Subscription ID: ****
Address: *********
Port: 6543
Protocol: grpc-tcp
Profile:
Connection: 2845
State: Connected
Explanation:

pe1-sth1#sh telemetry ietf subscription 281 receiver
Telemetry subscription receivers detail:

Subscription ID: ****
Address: **********
Port: 6543
Protocol: grpc-tcp
Profile:
Connection: 2848
State: Connected
Explanation:

We have tried different receivers and different vrfs, but still we cannot get more than 2 working.
Is there a “hidden” limitation ?

[M02@rt37]

Hello @RahmaSallm 

There is no hidden limitation in IOS-XE that limits the number of telemetry subscriptions that can be configured on a device. However, there are some practical limitations that may affect the ability of the device to successfully establish more than two telemetry subscriptions.

One possible factor that could be limiting the number of telemetry subscriptions is the available system resources. The device may not have enough available CPU, memory, or other resources to support more than two telemetry subscriptions.

Enable debug logging for the telemetry service using the "debug telemetry service" command, and review the logs for any error messages that could indicate the cause of the connection issue.