1.6 drop_transaction_data algorithm seems incorrect

[hikinggrass]

OCPP Version

OCPP1.6

Describe the bug

The drop_transaction_data data algorithm in lib/ocpp/v16/utils.cpp should drop every second message (except the first and last) but in my testing seems to behave a bit stragely. When I tested it with 5 messages it kept message 1, 4 and 5 but I would expect it to keep 1, 3 and 5

To Reproduce

No response

Anything else?

No response