changing ffmpeg framerate with " -r " not recognized?

[pxstein]

I 2-pass encode an existing *.mp4 into a (smaller) *.mp4 with the following command:

ffmpeg.exe -i "testffmpeg.mp4" -c:v libx264 -preset slow -b:v 1900k -s 1440x810 -pass 1 -g 30 -r 30 -an -f null NUL && ffmpeg.exe -i "testffmpeg.mp4" -c:v libx264 -preset slow -g 30 -r 30 -b:v 1900k -s 1440x810 -c:a libmp3lame -b:a 148k -pass 2 "testffmpeg_out.mp4"

which yields the output (for 1-pass) shown at the bottom.

Why are there such errors?

If I omit the " -r 30" parts the command works.

Do I have to specify " -r 30" in the first AND second pass command or only in one?

Output #0, null, to 'NUL':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
title : ****
artist : ****
date : 2019
comment : ***
encoder : Lavf58.29.100
Stream #0:0(und): Video: h264 (libx264), yuv420p, 1440x810 [SAR 1:1 DAR 16:9], q=-1--1, 1900 kb/s, 30 fps, 30 tbn, 30 tbc (default)
Metadata:
handler_name : ISO Media file produced by Google Inc.
encoder : Lavc58.54.100 libx264
Side data:
cpb: bitrate max/min/avg: 0/0/1900000 buffer size: 0 vbv_delay: -1
[libx264 @ 00000000024f49c0] non-strictly-monotonic PTS
Last message repeated 17 times
[null @ 0000000002682640] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 1 >= 1
[null @ 0000000002682640] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 2 >= 2
[libx264 @ 00000000024f49c0] non-strictly-monotonic PTS
[libx264 @ 00000000024f49c0] non-strictly-monotonic PTStrate=N/A speed=0.259x
[null @ 0000000002682640] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 4 >= 4
[null @ 0000000002682640] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 5 >= 5
[libx264 @ 00000000024f49c0] non-strictly-monotonic PTS
Last message repeated 1 times
[null @ 0000000002682640] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 7 >= 7
[null @ 0000000002682640] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 8 >= 8
[libx264 @ 00000000024f49c0] non-strictly-monotonic PTS
Last message repeated 1 times
[null @ 0000000002682640] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 10 >= 10
[null @ 0000000002682640] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 11 >= 11
[libx264 @ 00000000024f49c0] non-strictly-monotonic PTS
....

[ProWo]

Read https://trac.ffmpeg.org/wiki/Encode/H.264, Two-Pass Example