if the next track has a different sample rate, I go about 2 seconds without hearing the beginning of the track
I have a similar problem. Own Loxjie D30 v.2.
There are no problems when playing PCM, even when changing the frequency of tracks. But when playing DSD / SACD, the first track is always "lost" for 2-3 seconds, the rest are not, but only when playing sequentially. In MQA files, the first few seconds always disappear, although playback is on.
I turned to the DAC developer with this problem and received an answer: the loss of the first seconds is not a bug. This is how the device software works. This is done in order to avoid clicking when changing formats or frequencies. Alas, they will not change this algorithm in any firmware.
PS. I also asked the manufacturer to tell me more about which components are used in the device and which transformer is installed. I also asked to send a photo of the insides of the DAC. To which I received an answer: the scheme and the changed components are a trade secret and are not subject to disclosure. They refused to send the photo.
PS-2. Which DAC can you recommend to replace the D30? Such that it is not inferior in sound, and at the same time has no problems with "dropouts" in the DSD and MQA.
PS-3. I apologize for my English.