ESPNow ESP32 returning 'ESP_ERR_ESPNOW_ARG'

[davefes]

I am enhancing my ESPNow repeater project so that the remote and
repeater can go to deepsleep(). I plan to use DS3231s on the remote
and repeater so that I can wake them up each hour within +/- a few
seconds to obtain end-to-end comms.

During testing I can get the remote to run without errors when there
are no peers. However, the repeater has a very long script where I
am doing multiple e0.recv() and e0.send() ... the calls to e0.recv()
will timeout (10 secs) when there is no host and 4 * e0.send() work
without error, but a 5th e0.send() gives the following error:

E (36810) ESPNOW: Invalid argument! Error during execution: (-12390, 'ESP_ERR_ESPNOW_ARG')

That 5th e0.send() is the same format as the others.

Is there some issue with the number of Falses that can be returned
by e0.send()?

Thanks

[davefes]

Further testing indicates that one is not allowed to put an empty string in e0.send(), ie

remote_status = '' #  empty string

eo.send(remote_mac, remote_status, True)

which I was doing in stand-alone device testing.

[glenn20]

Yes - this is a constraint of the espressif ESPNOW api.

[davefes]

Thank you.