i am doing "transfer 4..  0.2  4..  0.1" which, after a second responds with "Error: transaction was not constructed"

the log file in addition has "cryptonote_tx_utils.cpp:242 Destinations have to have exactly one output to support encrypted payment ids" right before that

and a DEBUG saying "Encrypting payment id <37cc69754b0c871d>" right before that in turn. however, i did not enter any payment id

does it consider the last amount i provide a payment id?

(this is with a trezor, in case that's relevant)

also, it happens only after "account switch 1". on "account switch 0" the issue doesn't arise

Transactions to standard addresses automatically get assigned a random short payment id if none is specified.

I'll try to repro here.

sweet

Seems to work for me, but without a trezor.

maybe it's something about the outputs used

you did an account switch?

Yes

Payment ID stuff ought not depend on outputs used.

here it's using one input. might be relevant

so there's one input of .45 that's used for both outputs

let me see if things change using a different index explicitly

it doesn't

You're running a recent monero version I assume ?

monero-x86_64-linux-gnu-v0.17.1.9

when changing at least the first recipient to a 8.. address, it works

WORKS: transfer 8..  0.02  4..  0.01

WORKS: transfer 4..  0.02  8..  0.01

WORKS: transfer 8..  0.02  8..  0.01

DOESNT: transfer 4..  0.02  4..  0.01

just before payment id, log says the following, indicating that things might be treated somehow differently depending on the type of address:  cryptonote_tx_utils.cpp:76    destinations include 2 standard addresses and 0 subaddresses

They do. Subaddresses don't get the default payment id.