Rtd server terminated by Excel

Hello,

I seem to have stumbled upon this issue:
https://github.com/Excel-DNA/ExcelDna/blob/master/Source/ExcelDna.Integration/ExcelRtdServer.cs#L394

=> my RTD server is stopping

The setup on this Excel (2016, 32 bits) has other ExcelDna plugins, and when the spreadsheet is launched, there are some heavy computations that freeze Excel for some period (maybe up to 30 sec)

I tried to increase the HeartbeatInterval from 15sec to 60sec
The issue seem to be gone, but I'm not sure if this solved the issue
I'm not sure if I'm targeting the right cause

Also, when enabling ExcelDna logs, I found multiple occurences of:
`[WRN] Heartbeat callback while Notified in RTD server MyRtdServer - retrying UpdateNotify ExcelDna.Integration`

Not sure what it means.

Any help is appreciated

(BTW: I'm _still_ using ExcelDna 1.6 + .Net Framework)