I get the same error on mdash.net and curl.
To check if I did something wrong I download again the example from your link, build it with mos build, flash it to a different esp8266(flash is successfully) and try to send it again via OTA.
{
"code": -1,
"message": "-1 Image too big"
}
Same message appears.
This is what I get into console:
[Jan 28 20:48:36.847] mg_rpc.c:293 OTA.Begin via WSS_out 148.251.54.236:443
[Jan 28 20:48:36.854] mgos_ota_core.c:253 Starting, timeout 600, commit timeout 600, mem 39064
[Jan 28 20:48:37.212] mg_rpc.c:293 OTA.Write via WSS_out 148.251.54.236:443
[Jan 28 20:48:37.270] mg_rpc.c:293 OTA.Write via WSS_out 148.251.54.236:443
[Jan 28 20:48:37.282] mgos_ota_core.c:489 FW: smartlight esp8266 1.0 20200128-181300
[Jan 28 20:48:37.295] esp_ota_backend.c:152 Slot 1, FW: smartlight.bin -> 0x200000, FS fs.bin -> 0x48000
[Jan 28 20:48:37.307] mgos_ota_core.c:506 0.15% total, esp_init_data_default_v08.bin 128 of 128
[Jan 28 20:48:37.326] esp_ota_backend.c:231 Cannot write fs.bin (262144) @ 0x48000: max size 131072
[Jan 28 20:48:37.334] mgos_ota_core.c:811 Update finished, result -1 (Image too big)
[Jan 28 20:48:37.715] mg_rpc.c:293 OTA.Write via WSS_out 148.251.54.236:443
[Jan 28 20:48:37.970] mg_rpc.c:293 OTA.Write via WSS_out 148.251.54.236:443
[Jan 28 20:48:38.214] mg_rpc.c:293 OTA.End via WSS_out 148.251.54.236:443
Is it possible to send me your fw.zip to see if that works?