This is the second week in a row without a Windows 10 Mobile Insider Preview build for the Fast ring. Last week, Microsoft released build 15019 only for PCs, which brought, among other features, the new Game Mode. Today, the company released build 15025, and again it isn"t available for Windows 10 Mobile.
According to a tweet by Dona Sarkar, chief of the Windows Insider Program, the lack of mobile builds for Windows Insiders in the Fast ring is due to an unknown bug:
Finally, Sarkar hinted that the bug could block Windows 10 Mobile from participating in the bug bash, which starts next Friday, February 3. To participate in the bug bash, it"s necessary to be running the latest version of the Insider Preview build, currently build 15025. Unless Microsoft manages to get over this bug, don"t expect a bug bash for Windows 10 Mobile Insider Preview this week.
Source: Dona Sarkar via MSPoweruser