Hi Petr
To my knowledge there is no easy way to get a backup of the Firmware from the camera before attempting to upgrade or trying to resolved problem with Firmware.
I have ordered more than 50 cameras made by these Chinese manufacturer all with different Firmware and did see some improvement over the last 5 years.
The most reliable source to get the Firmware is most of time is directly from the Chinese vendor( you bought the camera from ) when they want to cooperate with you if you buy a lot from them or when they see potential future sale. Sometime they want proof that you have the camera so i did email them a picture showing the perticular version form the camera info web page.
They seam reluctant to supply Firmware because it is a ( double edge sword )it could possibly be good or brick your camera if it`s the wrong Firmware or done incorrectly and they got blamed .
For my parts i did received from at least 5 different vendor different Firmware asking for backup of the original Firmware and in some case what they have provided me were more recent ( date )most of time fixing/adding feature or not so obvious change ( probably fixing unseen bug ) .
The most recent feature been the ( 6 Languages ), the rule that i have seen is if the 3 first set is the same as the original Firmware you can upgrade safely ( it should be the Right Firmware for the device you try to upgrade ) but there are exception example: V19.1.27.16.3-20191216 should be possible with V19.1.27.15.19-20191129 because of the V19.1.27 but because of the date i would not be sure ( they might be risk or lost feature ).
Some vendor did ask honestly from their supplier for Firmware but got told the Firmware does not exist anymore , look like they do not know themself because i did ask for Firmware V20.1.13 and they say not available.
But to my surprise when i did upgrade a camera with original Firmware V20.1.12 the Upgrade did change the version in the camera from V20.1.12 to V20.1.13 and did added one feature.
So asking for Firmware V20.1.13 really does not exist , as the version was marked V20.1.12 and asking they were not positive this was going to be ok / safe .
Another source of Firmware are the web support site of the different vendor .
Example Those cam are the same but rebranded to different vendor like : IEGEEK.COM , sv3c.com , HQCAM.cn all those site do have Firmware directly accessible with no restriction from their support section.
The official site for Firmware , Program utility Manual is:
www.ipcam.xin but this is unbranded with no or poor vendor identification.
Over my 5 years and all my aventure in Firmware i have bricked 2 and saved upgraded 20 on a approximaly 80 mix of Cameras not a bad record.
i will try to upload to the IPCAMTALK support the Firmware V19.1.27.15.19-20191129 as this is the closest from your original.
Normally there is a basic protection in the Firmware that prevent Bricking as ( at the end of upgrade it would say succesfull ) but in reality did not change anything ( nothing upgraded ).
But do not count on it ( meaning there is always risk in Firmware upgrade )in one instance it did upgraded but i did lost the P2P so i couldnot see the cam on the PHONE APP anymore.
And because of the version change it did not want to return to the previous version ( always say succesfull but doing nothing ) , so in that perticular time i did rename the file version ( trick the Firmware to the previous version ) and the camera did return to normal and everything working normally in the last 2 years.
So good luck.
Martial