This problem is a side-effect of the way in which dependent USING actually works. When you declare that field LKINFO can be based on WKINFO, you are effectively telling HLASM it can assume that R13 points to LKINFO-(WKINFO offset from R13). So when it goes past that offset, it assumes it can use R13 as a base register.
There has been a requirement to do something to make this safer to use (while remaining compatible) for a very long time, and this was finally addressed by APAR PH42816 early this year. That adds new lower and upper limits on the USING statement, which apply both to 12-bit and 20-bit displacements, so you can ensure that a USING statement will not be used to address data outside the intended range. However, you should also limit the range of the overall USING for the area that includes that dependent range, otherwise you will still have multiple USINGs for the same range. For details, see the APAR page: https://www.ibm.com/support/pages/apar/PH42816 The weird USING heading may be in error, in that some problems with dependent USING headers were also fixed by PH42816 and earlier APAR PH42050 (which added 20-bit displacement support for dependent USING). Jonathan Scott, HLASM IBM Hursley, UK
